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Fuel Tankering: Economic Benefits and Environmental Impact for Flights Up to 1500 NM (Full Tankering) and 2500 NM (Partial Tankering)

Fuel Tankering: Economic Benefits and Environmental Impact for Flights Up to 1500 NM (Full... aerospace Article Fuel Tankering: Economic Benefits and Environmental Impact for Flights Up to 1500 NM (Full Tankering) and 2500 NM (Partial Tankering) , † † † † † Laurent Tabernier * , Esther Calvo Fernández , Andreas Tautz , Robin Deransy and Peter Martin European Organisation for the Safety of Air Navigation—EUROCONTROL, 91220 Brétigny/Orge, France; esther.calvo-fernandez@eurocontrol.int (E.C.F.); andreas.tautz@eurocontrol.int (A.T.); robin.deransy@eurocontrol.int (R.D.); peter.martin@eurocontrol.int (P.M.) * Correspondence: laurent.tabernier@eurocontrol.int † Authors contributed equally to this work. Abstract: The majority of emissions from aviation come from the combustion of the fuel required to operate each flight. Keeping the fuel consumption required for a safe flight to the absolute minimum is therefore the simplest and most effective way to ensure that emissions from that flight are kept to a minimum. In practice, however, the fuel load is determined by each aircraft operator on the basis of a number of criteria maximizing first cost efficiency, rather than fuel savings. In this context, tankering is the practice of carrying more fuel than is necessary for the safe execution of the flight to avoid or minimize refueling at the destination airport. It offers an economic advantage when there is a significant difference in fuel prices between the departure and arrival airports, but considerably increases the amount of emissions produced, because the more fuel an aircraft carries, the heavier it is, and carrying this extra weight increases its fuel consumption. This paper presents the steps followed by EUROCONTROL in conducting a first study to estimate the number of times this practice would Citation: Tabernier, L.; Fernández, offer an economic benefit and the amount of extra CO emissions that would result. This study, E.C.; Tautz, A.; Deransy, R.; Martin, P. limited to flights up to 1500 and 2500 NM, corresponding mainly to short and medium-haul flights, Fuel Tankering: Economic Benefits estimates that, in 2018, 21% of ECAC (In this paper, ECAC refers to the geographical region defined and Environmental Impact for Flights by the 44 member states that signed the European Civil Aviation Conference) flights would perform Up to 1500 NM (Full Tankering) and fuel tankering beneficially. This would represent a net saving of 265 M  per year for the airlines, 2500 NM (Partial Tankering). but the burning of 286,000 tonnes of additional fuel (equivalent to 0.54% of ECAC jet fuel used), or Aerospace 2021, 8, 37. https:// 901,000 tonnes of CO per year. At a time when aviation is challenged for its contribution to climate doi.org/10.3390/aerospace8020037 change, the use of fuel tankering for economic reasons is therefore highly questionable. Academic Editor: David Raper Received: 14 December 2020 Keywords: fuel tankering; CO emissions; economic benefit; fuel price Accepted: 26 January 2021 Published: 31 January 2021 Publisher’s Note: MDPI stays neutral 1. Introduction with regard to jurisdictional claims in As aviation is a highly competitive market, airlines must do everything possible to published maps and institutional affil- minimize their operating costs, in particular regarding fuel cost, which account for 17 to iations. 25% of their operating expenses [1]; this goes even up to 50% for some low-cost carriers. Furthermore, as the majority of aviation emissions come from the combustion of the fuel needed to operate each flight, it would seem logical that keeping the fuel consumption required for each flight to the absolute safe minimum is the simplest and most effective way Copyright: © 2021 by the authors. to ensure that both the emissions from that flight and the total cost of the fuel embarked Licensee MDPI, Basel, Switzerland. are minimized. This would mean carrying as little fuel as possible for the safe execution of This article is an open access article each flight. This is not the case. distributed under the terms and In practice, safety and special considerations at the destination airport aside, the fuel conditions of the Creative Commons load is determined by each aircraft operator according to a number of criteria that maximize Attribution (CC BY) license (https:// cost savings rather than fuel savings. creativecommons.org/licenses/by/ Fuel tankering is a practice used in this context. 4.0/). Aerospace 2021, 8, 37. https://doi.org/10.3390/aerospace8020037 https://www.mdpi.com/journal/aerospace Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 In practice, safety and special considerations at the destination airport aside, the fuel Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 load In p is de ract term ice, ined b safety y e and sp ach aircr ecia al con ft opserat ider or acco ations at rdi tn hg t e d oe a num stination ber of crit airport as eriide, a th t at h m e fu ax- el Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 load In p is de ract term ice, ined b safety y e and sp ach aircr ecia al con ft opserat ider or acco ations at rdi tn hg t e d oe a num stination ber of crit airport as eriide, a th t at h m e fu ax- el imize cost savings rather than fuel savings. Aerospace 2021, 8, 37 2 of 16 imize load In p is d cost savings rather e ract term ice, ined b safety y e and sp a c than fue h aircr ecia al con lft s op avings. serat ider or acco at ions at rdi tn hg t e d oe a num stination ber of crit airport as eriide, a th t at h m e fu ax- el Fuel tankering is a practice used in this context. In practice, safety and special considerations at the destination airport aside, the fuel imize load Fuel ta is d cost savings rather etenkeri rmined b ng is ya e pra a c than fue hc aircr tice used i alft s op avings. n erat thior acco s context. rdin g to a number of criteria that max- 2. Wh imize load 2. What In p is d at Is cost savings rather Is e ract te Fu Fuel rm ice, el ined b s T Tankering a afet nky y er e and sp ing a c than fue h aircr ecia al con lft s op avings. serat ider or acco at ions at rdi tn hg t e d oe a num stination ber of crit airport as eriide, a th t at h m e fu ax- el Fuel tankering is a practice used in this context. 2. Wh imize load Fuel ta is d at Is cost savings rather ete Fu nkeri rm el ined b T n ag is nky er a e pra ing a c than fue h c aircr tice used i alft s op avings. n erat thior acco s context. rdin g to a number of criteria that max- Fuel tan Fuel tankering kering is is a pr a practice actice whereby whereby an an aircr aircraft aft c carries arries more fuel than required more fuel than required for for its its 2. Wh imize Fuel ta at Is cost savings rather Fu nkeri el T n ag is nker a pra ing than fue ctice used i l savings. n this context. safe flight in order to reduce or avoid refueling at the destination airport [2]. safe fl Fuel tan ight in k order t ering is o re a pr du actice ce or avoid whereby refue an ling aircr at a t ft c hea dest rries in more fuel than required ation airport. [2] for its 2. Wh Fuel ta at Is Fu nkeri el T n ag is nker a pra ing ctice used in this context. Fuel tan Fuel tankering kering is can a pr be actice donewhereby for two reasons: an aircraft carries more fuel than required for its safe fl Fuel tank ight in order t ering can o re be done duce or avoid for two refue reaso ling ns: at the destination airport. [2] 2. What Is Fuel Tankering safe fl Fuel tank Fuel tan ight in k order t erin ering is g can o re a pr be done du actice ce or avoid for two whereby refue reaso an ling aircr ns: at a t ft c hea dest rries in more fuel than required ation airport. [2] for its When it is operationally not possible or desirable to refuel at the destination airport, ● When it is operationally not possible or desirable to refuel at the destination airport, 2. What Is Fuel Tankering Fuel tankering is a practice whereby an aircraft carries more fuel than required for its safe fl Fuel tank ight in order t ering can o re be done duce or avoid for two refue reaso ling ns: at the destination airport. [2] due to circumstances, such as the following: ● When due to c it is op ircum eration stances a,lly su no ch t possib as the fo le or llow die ng: sira ble to refuel at the destination airport, safe fl Fuel tank Fuel tan ight in k order t erin ering is g can o re a pr be done du actice ce or avoid for two whereby refue reaso an ling aircr ns: at a t ft c hea dest rries in more fuel than required ation airport. [2] for its ● When due to c it is op ircum eration stances a,lly su no ch t possib as the fo le or llow die ng: sira ble to refuel at the destination airport, social disruption;  social disruption; safe fl Fuel tank ight in order t ering can o re be done duce or avoid for two refue reaso ling ns: at the destination airport. [2] ● When it is operationally not possible or desirable to refuel at the destination airport, due to circumstances, such as the following: technical failures of the refueling installation;  s te ochnica cial disru l fail pures tion; of t he refueling installation; Fuel tankering can be done for two reasons: ● When due to c it is op ircum eration stances a,lly su no ch t possib as the fo le or llow die ng: sira ble to refuel at the destination airport, fuel shortages;  social disruption;  t fue echnica l shor l f tage ailures s; of the refueling installation; ● When it is operationally not possible or desirable to refuel at the destination airport, due to circumstances, such as the following: contaminated fuel at destination airport;  s t fue e ochnica cia l sho l dir sru l f tage ail pures ti s; on; of t he refueling installation;  contaminated fuel at destination airport; due to circumstances, such as the following: very short turnaround times;  social disruption;  t fue cont echnica l sho aminat r l f tage aed ilures s; fu el of t at de he ref stin u at elion ing airp insto ar llta ; tion;  very short turnaround times; risks of delays.  s te ochnica cial disru l fail pures tion; of t he refueling installation;  fue cont very short turna risk ls o sho am f de inat rtage lay ed s; s fu . r el ound ti at dest mes; ination airport;  t fue cont echnica l sho aminat r l f tage aed ilures s; fu el of t at de he ref stin u at elion ing airp insto ar llta ; tion;  T o achieve very short turna risks ofsavings delays. when round ti themes; cost of fuel and associated services at the departure ● To achieve savings when the cost of fuel and associated services at the departure  airport fue cont very short turna risk is ls o sho am significantly f de inat rtage lay ed s; s fu . r el ound ti lower at dest than mes; inatat ion the airp destination ort; airport. ● airp To ach orti eve is si savings when gnificantly lowe the cost r than at of th fue e dest l and in at assoc ion ai iated service rport. s at the departure  cont very short turna risks o am f de inat lay eds fu . r el ound ti at dest mes; ination airport; ● To ach There ar ieve e two savings when types of fuel the cost tankering: of fuel and associated services at the departure airport is significantly lower than at the destination airport. There are two types of fuel tankering:  very short turnaround times;  risks of delays. ● airp To ach orti eve is si savings when gnificantly lowe the cost r than at of th fue e dest l and in at assoc ion ai iated service rport. s at the departure There are two Full (fuel) tankering, types owhich f fuel tankerin consistsg: in transporting all the fuel needed for the return ● Full (fuel) tankering, which consists in transporting all the fuel needed for the return  risks of delays. ● To achieve savings when the cost of fuel and associated services at the departure airport is significantly lower than at the destination airport. flight from the departure airport to avoid refueling at the destination airport, and There are two types of fuel tankering: ● f Ful light f l (fue rom l) t the departure ankering, which ai cons rport to a ists in v t oid refuel ransportiing al ng at l the fuel the desti needed f nation ai orport, r the return and ● airp To ach orti eve is si savings when gnificantly lowe the cost r than at of th fue e dest l and in at assoc ion ai iated service rport. s at the departure There are two Partial (fuel) tankering, types of fue which l tankerin consists g: in transporting only part of the fuel needed for ●● Pa f Ful light f rtia l (fue l r(om fl) u t e the departure a l) n t k aering nkeri,n wh g, whi ich ai cons rport to a ch consi ists in sv ts in t oid refuel rantsporti ransping al o nr g a tint l the fuel g the desti only pa needed f r nta o tion ai f theo frport, r the return uel nea en dd ed airport is significantly lower than at the destination airport. the return flight and performing only partial refueling at destination. There are two types of fuel tankering: ● Full (fuel) tankering, which consists in transporting all the fuel needed for the return ● for the r Pa flight f rtial r(om f eu turn e the departure l) t flight ankeriand pe ng, whi ai rformin rport to a ch consi g on sv ts in oid refuel ly part tranis ap l re io nr g a tfu ineling tg the desti onl at y p dest ar nta o itn ion ai f t at h ion. e frport, u e l nea en dd ed There are two types of fuel tankering: Under the European Union Aviation Safety Agency regulations (CAT.OP.MPA.150 Fuel ●● Pa f Ful light f rtia l (fue l r(om fl) u t e the departure a l) n t k aering nkeri,n wh g, whi ich ai cons rport to a ch consi ists in sv ts in t oid refuel rantsporti ransping al o nr g a tint l the fuel g the desti only pa needed f r nta o tion ai f theo frport, r the return uel nea en dd ed for the return flight and performing only partial refueling at destination. Under the European Union Aviation Safety Agency regulations (CAT.OP.MPA.150 policy), before departure, the captain must ensure that every flight carries sufficient fuel ● Full (fuel) tankering, which consists in transporting all the fuel needed for the return ● for the r Pa flight f rtial r(om f eu turn e the departure l) t flight ankeriand pe ng, whi ai rformin rport to a ch consi g on sv ts in oid refuel ly part tranis ap l re io nr g a tfu ineling tg the desti onl at y p dest ar nta o itn ion ai f t at h ion. e frport, u e l nea en dd ed Under the European Union Aviation Safety Agency regulations (CAT.OP.MPA.150 Fuel policy), before departure, the captain must ensure that every flight carries sufficient for the planned operation and reserves to cover deviations from the planned operation: ● Pa flight f rtial r(om fue the departure l) tankering, whi airport to a ch consisv ts in oid refuel transpio nr g a tintg the desti only par nta o tion ai f the frport, uel nea en dd ed for the return flight and performing only partial refueling at destination. Fuel po Under t licy), h before dep e European Un arture, the c ion Avaiat ptain must ion Safety ens Agenc ure ty h r at e every f gulation light s (C carr AT.OP. ies s MPA uffic.ient 150 fuel for the planned operation and reserves to cover deviations from the planned opera- ● for the r Partial (f eu turn el) t flight ankeriand pe ng, whi rformin ch consi g on sts in ly part tranis ap l re ortfu ineling g onl at y p dest art o in f t at h ion. e fu e l needed Taxi fuel: The fuel necessary for taxi, which should not be less than the amount ti fue Fuel po on: l fUnder t or t lic hy), e ph before dep lanned op e European Un e arrture, the c ation ioand re n Avaiat ptain must ser ion ves t Safet o cov y ens Agenc er ur dev e ty h i r at at eions every f gulafr tion om light s (C th carr e p AT.OP. lann ies e s MPA d op uffic.er ient 150 a- for the return flight and performing only partial refueling at destination. expected to be used prior to take-off; Fuel po Under t licy), h before dep e European Un arture, the c ion Avaiat ptain must ion Safety ens Agenc ure ty h r at e every f gulation light s (C carr AT.OP. ies s MPA uffic.ient 150 ti fue on: l for the planned operation and reserves to cover deviations from the planned opera- ● Taxi fuel: The fuel necessary for taxi, which should not be less than the amount Trip fuel: The fuel required from the start of take-off, through climb, cruise, descent, ti fue Fuel po on: l fUnder t or t lic hy), e ph before dep lanned op e European Un e arrture, the c ation ioand re n Avaiat ptain must ser ion ves t Safet o cov y ens Agenc er ur dev e ty h i r at at eions every f gulafr tion om light s (C th carr e p AT.OP. lann ies e s MPA d op uffic.er ient 150 a- ● expected to be used pr Taxi fuel: The fuel nec ior t essary o take for t -off; axi, which should not be less than the amount and approach to touchdown at destination; Fuel policy), before departure, the captain must ensure that every flight carries sufficient ti fue on: l for the planned operation and reserves to cover deviations from the planned opera- ● Taxi fuel: The fuel necessary for taxi, which should not be less than the amount ● Trip f expected to be used pr uel: The fuel requior t iredo from t take-off; he start of take-off, through climb, cruise, descent, Reserve fuel consisting of: fuel for the planned operation and reserves to cover deviations from the planned opera- tion: ●● Trip f expected to be used pr Taxi fuel: Th uel: Thee fuel nec fuel requior t ire essary do from t take for t -off; ha e st xi, awhich sho rt of take-of ufld not be less than the am , through climb, cruise, desc ount ent, and approach to touchdown at destination; tion: # Contingency fuel (3 to 5%): This fuel is carried to cover unforeseen variations ● Taxi fuel: The fuel necessary for taxi, which should not be less than the amount ●● Rese and Trip f expected to be used pr ap rve f up elr : The oach uel c fue t onsist o t lo re uchdow iqu ngior t ire ofd : o from t n at take de -off; h st e st inat ar it o of t n; ake-off, through climb, cruise, descent, from the planned operation. For example, different winds or temperatures ●● Trip f expected to be used pr Taxi fuel: Th uel: Thee fuel nec fuel requior t ire essary do from t take for t -off; ha e st xi, awhich sho rt of take-of ufld not be less than the am , through climb, cruise, desc ount ent, ● Rese and ap rve f proach uel c t onsist o touchdow ing of: n at destination; ○ Contingency fuel (3 to 5%): This fuel is carried to cover unforeseen variations from forecast, or air traffic control restrictions on levels and speed. It can be ● and Trip f expected to be used pr ap up elr : The oach fue to t lo re uchdow quior t iredo from t n at take de -off; h st e st inat ar it o of t n; ake-off, through climb, cruise, descent, ● Reserve fuel consisting of: ○ from the plan Contingency ned operatio fuel (3 to 5%n. For ex ): This fu ample, el is carr diffe ied rent to co wiver un nds or t fore emperat seen var ureisat from ions used any time after dispatch (once aircraft moves under its own power). It ●● Rese and Trip f ap rve f up elr : The oach uel c fue t onsist o t lo re uchdow iqu ngire ofd : from t n at deh st e st inat ar it o of t n; ake-off, through climb, cruise, descent, ○ Contingency fuel (3 to 5%): This fuel is carried to cover unforeseen variations forec from the plan ast, or air traffic contr ned operation. For ex ol restrict ample, ions on levels different and winds or t speed. It can emperat be used ures from any cannot be planned to use before. More likely, it is used for delays on departure and approach to touchdown at destination; ● Reserve fuel consisting of: ○ forec from the plan Contingency ast, or air traffic contr ned operatio fuel (3 to 5%n. For ex o ):l restrict This fu ample, el ions is on levels carr diffe ied rent toand co wiver un nds or t speed. It can fore emperat seen be used var ureisat from ions any time after dispatch (once aircraft moves under its own power). It cannot be or arrival; ● Reserve fuel consisting of: ○ Contingency fuel (3 to 5%): This fuel is carried to cover unforeseen variations time after forec from the plan ast, or air traffic contr dispatch ned operatio (once n. For ex oairc l restrict raft move ample, ions on levels s un diffe der rent its o and winds or t speed. It can wn power). I emperat be used t cannot be ures from any planned to use before. More likely, it is used for delays on departure or arrival; # Alternate fuel: The fuel to cover a possible “Go around” or a landing at an ○ from the plan Contingency ned operatio fuel (3 to 5%n. For ex ): This fu ample, el is carr diffe ied rent to co wiver un nds or t fore emperat seen var ureisat from ions ○ planned time after forec Altern ast, or air traffic contr at to u e fu dispatch el se before : The fu(once el t . Mo o c r oairc e o l restrict l vie kel raft move r a p y, o it i ions sss ib u on levels ls un e sed “Gfor de der o ar its o ound and lay speed. It can sw ” or on dep n power). I a land artur ing e or be used t at cannot be an arr alt ival; any er- alternate airport; time after forec from the plan ast, or air traffic contr dispatch ned operatio (once n. For ex oairc l restrict raft move ample, ions on levels s un diffe der rent its o and winds or t speed. It can wn power). I emperat be used t cannot be ures from any ○ planned na Alt te ai ernat rport; to u e fuel se before : The fuel t . Mo o c re o l vie kel r a p y, o it i sss ib u le sed “Gfor de o around lays” or on dep a land artur ing e or at an arr alt ival; er- # Final reserve: For 30 min at International Standard Atmosphere 1500 feet above ○ planned time after forec Altern ast, or air traffic contr at to u e fu dispatch el se before : The fu(once el t . Mo o c r oairc e o l restrict l vie kel raft move r a p y, o it i ions sss ib u on levels ls un e sed “Gfor de der o ar its o ound and lay speed. It can sw ” or on dep n power). I a land artur ing e or be used t at cannot be an arr alt ival; any er- ○ na Fina te ai l rese rport; rve: For 30 min at International Standard Atmosphere 1500 feet above the alternate airport; time after dispatch (once aircraft moves under its own power). It cannot be ○ planned na Alt te ai ernat rport; to u e fuel se before : The fuel t . Mo o c re o l vie kel r a p y, o it i sss ib u le sed “Gfor de o around lays” or on dep a land artur ing e or at an arr alt ival; er- ○ t Fina he alt l rese ernat rve e:airp Forort 30; m in at International Standard Atmosphere 1500 feet above # Discretionary fuel (or 15 min of holding fuel if the flight is planned with planned to use before. More likely, it is used for delays on departure or arrival; ○○ na Alt t Fina he alt te ai ern l rese e at rport; rn e fu at rve e: el airp For : The fu ort 30; m el t in oat co Int vee r a p rnat o ion ssib all St e “G ano a dar rd ound Atm ” or ospa l here and 15 ing 00 at feet an ab alt ov ere - ○ Discretionary fuel (or 15 min of holding fuel if the flight is planned with no al- no alternate (go-around at destination, climb, cruise, descent, approach, and ○ na Alt te ai ernat rport; e fuel: The fuel to cover a possible “Go around” or a landing at an alter- ○○ t Fina Discret th ernat e alt l rese e ( eirn on gat o- rv ar e ar e: yairp For ound fueort 3 l (o 0 at ; m r 1 dest i5 n m at in i Int n of ho ation, ernat cl ldin ion imb g a,l cru St fuel an i if se, dar the fl desc d At e ight i n m t,o ap sp s here p planned roach, 150and 0with no al- feet lan ab dov ing e landing at the selected alternate airport); ○ na t Fina he alt te ai l rese e rport; rnat rve e:airp Forort 30; m in at International Standard Atmosphere 1500 feet above ○ Discret a te trnat the sel e ( ion g eo- cted al ar ar yound fue terna l (o atr 1 dest te 5airport) m in in of ho ation, ; cl ldin imb g , cru fuel i if se, the fl desce ight i nt, ap s p planned roach, and with no al- landing # Extra fuel, which should be at the discretion of the commander. ○○ t Fina Discret th ernat e alt l rese e ( eirn on gat o- rv ar e ar e: yairp For ound fueort 3 l (o 0 at ; m r 1 dest i5 n m at in i Int n of ho ation, ernat cl ldin ion imb g a,l cru St fuel an i if se, dar the fl desc d At e ight i n m t,o ap sp s here p planned roach, 150and 0with no al- feet lan ab dov ing e ○ a Extra t the sel fuel e, whi cted al ch shoul ternate dairport) be at the di ; scretion of the commander. In other words, fuel tankering is the practice of adding more fuel than what is required ○ t Discret a th e trnat the sel e alte ( eirn on g eat o- cted al ar e ar yairp ound fue terna ort l (o at ; r 1 dest te 5airport) m in in of ho ation, ; cl ldin imb g , cru fuel i if se, the fl desce ight i nt, ap s p planned roach, and with no al- landing ○ Extra fuel, which should be at the discretion of the commander. In other words, fuel tankering is the practice of adding more fuel than what is re- by the fuel policy for a safe flight. ○ Discretionary fuel (or 15 min of holding fuel if the flight is planned with no al- ○ a t Extra e trnat the sel fuel e (g eo- , whi cted al around ch shoul terna at dest te dairport) bie n a at tion, the di ; clim screti b, cru on of ise, the desc comma ent, ap nder. proach, and landing In other words, fuel tankering is the practice of adding more fuel than what is re- quired by the fuel policy for a safe flight. a te trnat the sel e (g eo- cted al around terna at dest te airport) ination, ; climb, cruise, descent, approach, and landing ○ Extra fuel, which should be at the discretion of the commander. 3. Purpose of This Study quired In by t othe hre w fuo el po rds, lic fuy fo el ta r a nk s ea rfe in f glight is th . e practice of adding more fuel than what is re- ○ a Extra t the sel fuel e, whi cted al ch shoul ternate dairport) be at the di ; scretion of the commander. In other words, fuel tankering is the practice of adding more fuel than what is re- 3. quPurpos ired by t e of he This S fuel potlic ud y fo y r a safe flight. Until now, the very few studies on fuel tankering [3–9] have focused mainly on its ○ Extra fuel, which should be at the discretion of the commander. 3. quPurpos ired In by t ote of he hre w This S fuo el po rds,t lic ud fuy fo eyl t a r a nk s ea rfe in f glight is th . e practice of adding more fuel than what is re- economic benefits for a single or a limited number of flight. 3. quPurpos ired In by t ote of he hre w This S fuo el po rds,t lic ud fuy fo eyl t a r a nk s ea rfe in f glight is th . e practice of adding more fuel than what is re- However, as illustrated on Figure 1, when a return flight between two airports A and 3. quPurpos ired by t e of he This S fuel potlic ud y fo y r a safe flight. B, carry part or all of the fuel needed for its return flight (B-A), an “extra” amount of fuel is 3. Purpose of This Study burnt just to carry that additional fuel on the first leg (A-B). This is because the additional 3. Purpose of This Study fuel carried when doing fuel tankering increases the weight of the aircraft and thus its fuel consumption, resulting in additional CO emissions. ICAO Doc 10013 [2] indicates Aerospace 2021, 8, x FOR PEER REVIEW 3 of 16 Until now, the very few studies on fuel tankering [3–9] have focused mainly on its economic benefits for a single or a limited number of flight. However, as illustrated on Figure 1, when a return flight between two airports A and B, carry part or all of the fuel needed for its return flight (B-A), an “extra” amount of fuel is burnt just to carry that additional fuel on the first leg (A-B). This is because the addi- tional fuel carried when doing fuel tankering increases the weight of the aircraft and thus its fuel consumption, resulting in additional CO2 emissions. ICAO Doc 10013 [2] indicates that “The extra fuel burn attributable to additional weight carried on board an aircraft is typically on the order of 2.5 to 4.5% of the additional weight, per hour of flight, depending on the characteristics of the aircraft.” Fuel tankering has therefore an environmental im- pact. As the demand to accelerate the decarbonization of transport becomes more and more pressing, it is relevant to estimate the extent of the environmental impact of fuel tankering. The purpose of this paper is to present the results of a first study whose aim Aerospace 2021, 8, 37 3 of 16 was to estimate what the impact of fuel tankering would be at ECAC level in 2018 on the basis of the actual collected data (i.e.,: fuel prices at airports in June 2018, and passenger load that f “The actor ext at ra that fuel time, burn etattributable c.). In the futto uradditional e, it would be weight intere carried sting ton o car boar ry o du an t sair ens craft itivitis y ana typically lyses t on o se the e tor he econom der of 2.5ic tolimit 4.5%s of of t the his pr additional actice by weight, varying per fuel hour prices and of flight, un depending der dif- on the characteristics of the aircraft.” Fuel tankering has therefore an environmental impact. ferent hypotheses of passenger load factor, etc. Figure 1. Example of extra fuel burn for a return flight between two airports with and without fuel Figure 1. Example of extra fuel burn for a return flight between two airports with and without tankering. fuel tankering. As the demand to accelerate the decarbonization of transport becomes more and more pressing, it is relevant to estimate the extent of the environmental impact of fuel tankering. The purpose of this paper is to present the results of a first study whose aim was to estimate what the impact of fuel tankering would be at ECAC level in 2018 on the basis of the actual collected data (i.e.,: fuel prices at airports in June 2018, and passenger load factor at that time, etc.). In the future, it would be interesting to carry out sensitivity analyses to see the economic limits of this practice by varying fuel prices and under different hypotheses of passenger load factor, etc. 4. Study The study was conducted with the following steps, data, and assumptions. 4.1. Steps of the Study STEP 1: Verify that fuel tankering is a common practice that deserves to be studied and that no regulatory instruments already exist to dissuade airlines from tankering fuel or to compensate for its impact on the environment; Aerospace 2021, 8, 37 4 of 16 STEP 2: Calculate the fuel tankering efficiency with EUROCONTROL Base of Aircraft Data (BADA) models based on typical types of aircraft flying in ECAC airspace and for all the possible distances flown; STEP 3: Calculate the number of flights for which full or partial tankering is opera- tionally possible; STEP 4: Estimate the economic opportunity of tankering. 4.2. Data Used and Assumptions The statistics required for the calculations were derived from June 2018 traffic in the ECAC area; The estimated tankering results for this month has been extrapolated to a year by applying a linear extrapolation based on the number of flights for which fuel tankering was feasible. However, the extrapolation made does not take account of any influence of seasonal traffic patterns; The study covered aircraft models representing 66% of flights in ECAC; Aircraft performance was based on EUROCONTROL BADA model. BADA is the international reference in aircraft performance modeling for trajectory prediction and simulation. Based on the best available reference data on aircraft performance, BADA reproduces realistically the geometric, kinematic and kinetic aspects of aircraft’s behaviour over the entire operational flight envelope and in all phases of flight; The optimal flight level calculated for performing full fuel tankering was used in the model. The following limits have been taken into account: Maximum take-off weight, Maxi- mum landing weight, Maximum fuel load of each aircraft type; An average 20 min was used for the taxi-out; This value was calculated using average taxi-out times provided by EUROCONTROL Central Office of Delay Analysis for the busiest European airports; The CO emission factor used is 3.15 kg CO per kg of fuel burn; 2 2 Fuel prices negotiated at 140 airports in ECAC from 2 major airlines were used; The payload was calculated with a load factor of 80.3% [10] and 124 kg/passenger; A profit threshold of  30 was used as a pivotal point in the decision to go into fuel tankering; but this is a very cautious assumption as some airlines use  15 as a pivotal point; A cost of  20/tonne has been set for a tonne of CO allowances; this is also a very conservative assumption because not every tonne of CO requires the purchase of CO allowances; In the tables presented in our study “Trip fuel” is composed of the following elements: Taxi + Climb Cruise Descent + Approach to Touchdown. The “Reserve fuel” is composed of the following elements: Contingency + Alternate + Final reserve; When, for a round trip, both full and partial fuel tankering were possible, our model always privileged full fuel tankering. 4.3. Flights Excluded from the Study Military flights performed by military aircraft and customs and police flights; search and rescue; state flights; Flights not performed under instrument flight rules (IFR) only. 4.4. Study Limitations Due to the coverage of airline negotiated fuel price data we were able to access, the study was limited to flights up to 1500 (Full tankering) and 2500 NM (Partial tankering). As a result, the aircraft models considered are mainly operated on short and medium-haul. Furthermore, due to the physical fuel capability of the aircraft models considered: # For full tankering, flight legs of more than 1500 NM were not considered, Aerospace 2021, 8, 37 5 of 16 # For partial tankering, flight legs of more than 2500 NM were not considered. The impact of fuel tankering for reasons other than fuel price differences at airports was not considered (e.g., shorten turnaround or fuel shortage). The possibility of tankering fuel for more than one leg, which the software of some airlines is able to calculate, has not been estimated. 4.5. STEP 1: Verify That Fuel Tankering Is a Common Practice That Deserves to Be Studied and That No Regulatory Instruments Already Exist to Dissuade Airlines from Tankering Fuel or to Compensate for Its Impact on the Environment We started by conducting a series of interviews of pilots from airlines, business aviation dispatchers and handling agents. They confirmed that fuel tankering was a practice commonly used by airlines. They reported that 15% of the time they are performing full fuel tankering, and another 15% for partial fuel tankering. They also reported that fuel tankering is done in 90% of cases for fuel price reasons, and only in 10% of cases for social disruption, technical failures at the refueling facility, fuel shortages, risks of delays, or contaminated fuel at destination airports. In fact, this practice is so common that, to assist the captain in calculating the optimum tankering, most airlines use operations centre software (e.g., Lido and Sabre) that ensures compliance with fuel policy but also takes into account the cost of fuel that the airline has negotiated at the airports it serves to determine the maximum amount of fuel that could be added on top if cost-effective. A patent has recently been published by Honeywell for a tool to further enhance fuel tankering and fully exploit its economic benefits [11]. Unexpectedly, in ICAO Doc. 10013 [2], which deals with “Operational Opportunities to Reduce Fuel Burn and Emissions”, the recommendation to reduce the use of fuel tankering is presented as a measure to reduce cost rather than highlighting the amount of additional emissions it generates, particularly CO emissions. Then, we investigated whether instruments already exist to limit its practice or com- pensate for its environmental impact. The only instrument currently in place that could have had this effect is the European Union Emissions Trading Scheme (EU ETS). However, the inclusion of aviation in the CO European EU ETS currently in place is not sufficient to limit the practice of tankering for economic reasons. First of all, Aviation EU ETS only covers flights within the European Union and therefore excludes flights for which one of the two airports served is located outside this area. For example, flights from Africa, America, Asia, China, Middle East, or Russia, are not subject to the EU ETS. In addition, as of today, 85% of the CO emission quotas of the aviation EU ETS, determined when the baseline was established, are still free of charge. Furthermore, as pointed out by Daley and Preston, in [12], care should be taken to ensure that the introduction of new policies does not amplify the practice of tankering. [12] quotes: “if fuel taxes were not introduced globally, economic distortions could occur, creating an incentive for airlines to uplift cheaper fuel—by tinkering—in countries where the tax did not apply, with the net effect that aviation emissions could increase—hereby negating the original purpose of the tax (Wit et al., 2004, p. 43)”. However, as we observed in STEP 2, even in this case, this phenomenon would be limited by the physical capability of the aircraft to perform tankering and the possibility for airlines to adapt their business model to this new tax and the new possible traffic patterns. The purpose of this study is not to address the influence that new policies could have on the practice of tankering. 4.6. STEP 2: Identify When Fuel Tankering Is Operationally Feasible in ECAC The capacity of aircraft to transport fuel is not infinite. Multiple factors influence the amount of fuel an aircraft can carry for a specific flight. It depends on the aircraft model, the type of engines it is equipped with, the size and options of the fuel tank fitted, its maximum take-off and landing weight, the distance flown, the specific conditions and situation at each airport and, most importantly, its payload. Aerospace 2021, 8, x FOR PEER REVIEW 6 of 16 4.6. STEP 2: Identify When Fuel Tankering Is Operationally Feasible in ECAC The capacity of aircraft to transport fuel is not infinite. Multiple factors influence the amount of fuel an aircraft can carry for a specific flight. It depends on the aircraft model, Aerospace 2021, 8, 37 6 of 16 the type of engines it is equipped with, the size and options of the fuel tank fitted, its maximum take-off and landing weight, the distance flown, the specific conditions and situation at each airport and, most importantly, its payload. The first step is therefore to estimate, for each type of aircraft, its capacity to carry The first step is therefore to estimate, for each type of aircraft, its capacity to carry different amounts of additional fuel (the amount of tankering in % of the fuel necessary different amounts of additional fuel (the amount of tankering in % of the fuel necessary for the return flight) over different distances, for different flight levels, and the amount of for the return flight) over different distances, for different flight levels, and the amount of extra fuel burn due to the transport of this additional fuel. This was established with the extra fuel burn due to the transport of this additional fuel. This was established with the help of BADA. help of BADA. Figure 2 is an example of the “extra” fuel burn for one of the most representative Figure 2 is an example of the “extra” fuel burn for one of the most representative aircraft models flying in ECAC for several distances and flight levels over which it can be aircraft models flying in ECAC for several distances and flight levels over which it can be operated. It can be seen that the % of extra fuel burnt on the first leg A to B, while carrying operated. It can be seen that the % of extra fuel burnt on the first leg A to B, while carrying the full fuel required for the return leg B to A, varies a lot depending on the flight level, the full fuel required for the return leg B to A, varies a lot depending on the flight level, distance flown, and the % of tankering carried (due to the additional weight). distance flown, and the % of tankering carried (due to the additional weight). Figure 2. % of extra fuel burnt for full fuel tankering on various flight distances for a specific aircraft model. Figure 2. % of extra fuel burnt for full fuel tankering on various flight distances for a specific aircraft model. Figure 2 also helps to determine the % of extra fuel burnt at a flight level by a specific Figure 2 also helps to determine the % of extra fuel burnt at a flight level by a specific aircraft model. aircraft model. Each aircraft weight has its own optimum flight level for a given distance. This is what is consider here, we determine the optimal flight level taking into account the new aircraft weight when performing full fuel tankering. However, when reading it, it should not be concluded that the lower % of “extra” fuel burnt at the lowest flight levels (e.g., FL 290) translates into lower overall fuel consumption compared to higher flight levels (e.g., FL 350). Indeed, at these flight levels, the aircraft is well below its optimum cruising level, and will therefore consume much more fuel than at flight levels closer to this optimum. It is therefore necessary to convert to absolute kg of Aerospace 2021, 8, x FOR PEER REVIEW 7 of 16 Each aircraft weight has its own optimum flight level for a given distance. This is what is consider here, we determine the optimal flight level taking into account the new aircraft weight when performing full fuel tankering. However, when reading it, it should not be concluded that the lower % of “extra” fuel burnt at the lowest flight levels (e.g., FL 290) translates into lower overall fuel con- sumption compared to higher flight levels (e.g., FL 350). Indeed, at these flight levels, the aircraft is well below its optimum cruising level, and will therefore consume much more Aerospace 2021, 8, 37 7 of 16 fuel than at flight levels closer to this optimum. It is therefore necessary to convert to ab- solute kg of total fuel burnt to determine the optimum flight level to be used for carrying total fuel burnt to determine the optimum flight level to be used for carrying the “extra” the “extra” fuel tankered. fuel tankered. Figure 3 shows that for a 600 NM flight of this aircraft model, the absolute minimum Figure 3 shows that for a 600 NM flight of this aircraft model, the absolute minimum fuel burnt for carrying all the fuel required for the return flight (“full fuel tankering”) will fuel burnt for carrying all the fuel required for the return flight (“full fuel tankering”) will be obtained if the flight is cruising at 36,000 ft (FL 360). The percentage of extra fuel burn be obtained if the flight is cruising at 36,000 ft (FL 360). The percentage of extra fuel burn compared to the fuel burn for one trip at its optimum flight level (36,000 ft or FL 360) compared to the fuel burn for one trip at its optimum flight level (36,000 ft or FL 360) compared to other possible flight levels is highlighted in Figure 4. This percentage of ad- compared to other possible flight levels is highlighted in Figure 4. This percentage of ditional fuel burn is useful in determining the threshold at which it will be cost effective additional fuel burn is useful in determining the threshold at which it will be cost effective to tanker fuel, as exp to tanker lai fuel, ned bel as explained ow. below. Figure 3. Total fuel burnt (kg) for full fuel tankering at various flight levels (hundreds of feet). Figure 3. Total fuel burnt (kg) for full fuel tankering at various flight levels (hundreds of feet). In this study, it was assumed that all flights would fly at their optimum flight level, but In this study, it was assumed that all flights would fly at their optimum flight level, in reality, this is not always possible due to limited en route capacity or flight level capping but in reality, this is not always possible due to limited en route capacity or flight level between two city pairs (e.g., Between Paris and Frankfurt, flights are capped at 23,000 ft capping between two city pairs (e.g., Between Paris and Frankfurt, flights are capped at (FL 230) in one direction and 24,000 ft (FL 240) in the other direction, and are therefore 23,000 ft (FL 230) in one direction and 24,000 ft (FL 240) in the other direction, and are burning even more fuel to carry the extra fuel compared to flying closer to 36,000 ft (FL 360) therefore burning even more fuel to carry the extra fuel compared to flying closer to 36,000 for this distance and weight. Consequently, in this study the extra fuel burn estimates due to tankering are very conservative. ft (FL 360) for this distance and weight. Consequently, in this study the extra fuel burn Let us take the example of one of the most representative short-medium haul European estimates due to tankering are very conservative. aircraft on a 600 NM round trip flight, a distance close to the average distance of 585 NM for ECAC flight, between two airports A and B (Figure 5). The total weight of the aircraft model chosen consists of 43.7 tonnes of empty operating weight, plus 17.6 tonnes of payload, and 4.5 tonnes of fuel consisting of 3.6 tonnes for the flight and 0.9 tonnes of reserve and taxi. This model has a maximum fuel load capacity of 23.5 tonnes of fuel, and a maximum take-off weight of 77 tonnes. Aerospace 2021, 8, x FOR PEER REVIEW 8 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 8 of 16 Aerospace 2021, 8, 37 8 of 16 Figure 4. % of extra fuel burnt for various flight distances for a specific aircraft mode with optimum flight cruise level determined. Let us take the example of one of the most representative short-medium haul Euro- pean aircraft on a 600 NM round trip flight, a distance close to the average distance of 585 NM for ECAC flight, between two airports A and B (Figure 5). The total weight of the aircraft model chosen consists of 43.7 tonnes of empty operating weight, plus 17.6 tonnes of payload, and 4.5 tonnes of fuel consisting of 3.6 tonnes for the flight and 0.9 tonnes of Figure 4. % of extra fuel burnt for various flight distances for a specific aircraft mode with optimum Figure 4. % of extra fuel burnt for various flight distances for a specific aircraft mode with optimum flight cruise level deter- reserve and taxi. This model has a maximum fuel load capacity of 23.5 tonnes of fuel, and flight cruise level determined. mined. a maximum take-off weight of 77 tonnes. Let us take the example of one of the most representative short-medium haul Euro- pean aircraft on a 600 NM round trip flight, a distance close to the average distance of 585 NM for ECAC flight, between two airports A and B (Figure 5). The total weight of the aircraft model chosen consists of 43.7 tonnes of empty operating weight, plus 17.6 tonnes of payload, and 4.5 tonnes of fuel consisting of 3.6 tonnes for the flight and 0.9 tonnes of reserve and taxi. This model has a maximum fuel load capacity of 23.5 tonnes of fuel, and a maximum take-off weight of 77 tonnes. Figure 5. Example for a 600 NM flight with no tankering. Figure 5. Example for a 600 NM flight with no tankering. When not doing tankering (Figure 5), the fuel consumption of this aircraft model over When not doing tankering (Figure 5), the fuel consumption of this aircraft model over tthis his d distance istance iis s 3 3.59 .59 ttonnes. onnes. O On n a arrival rrival a at t a airport irport B B, , tther here e iis s 0 0.7 .7 ttonnes onnes o of f r re eserve serve ffuel uel lleft, eft, and the total and the total weight of the weight of the airc aircraft raft does does not exceed 66 tonnes certified maxim not exceed 66 tonnes certified maximum um land landing ing weight weight fo for r a s a safe afe llanding. anding. By tanker By tankering ing all all the fuel n the fuel needed eeded fo for the r the return le return leg (B-A) g (B-A) from from airport airpA ort A over a over a 600 NM 600 flight (Figure 6), this flight burns 167 kg of fuel on top of the 3.59 tonnes of fuel burnt when NM flight (Figure 6), this flight burns 167 kg of fuel on top of the 3.59 tonnes of fuel burnt Figure 5. Example for a 600 NM flight with no tankering. not doing tankering. This represents 4.66% more fuel burnt. Consequently, if the fuel price when not doing tankering. This represents 4.66% more fuel burnt. Consequently, if the negotiated by its airline operator at the destination airport B is 4.66% more expensive than When not doing tankering (Figure 5), the fuel consumption of this aircraft model over at the departure airport A, and that the potential cost saving is above the profit threshold, it this distance is 3.59 tonnes. On arrival at airport B, there is 0.7 tonnes of reserve fuel left, might be worthwhile for this operator, from an economic point of view, to decide to tanker and the total weight of the aircraft does not exceed 66 tonnes certified maximum landing all the fuel necessary for the return flight (B-A) from the departure airport A. weight for a safe landing. By tankering all the fuel needed for the return leg (B-A) from airport A over a 600 NM flight (Figure 6), this flight burns 167 kg of fuel on top of the 3.59 tonnes of fuel burnt when not doing tankering. This represents 4.66% more fuel burnt. Consequently, if the Aerospace 2021, 8, x FOR PEER REVIEW 9 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 9 of 16 fuel price negotiated by its airline operator at the destination airport B is 4.66% more ex- fuel price negotiated by its airline operator at the destination airport B is 4.66% more ex- pensive than at the departure airport A, and that the potential cost saving is above the pensive than at the departure airport A, and that the potential cost saving is above the profit threshold, it might be worthwhile for this operator, from an economic point of view, profit threshold, it might be worthwhile for this operator, from an economic point of view, Aerospace 2021, 8, 37 to decide to tanker all the fuel necessary for the return flight (B-A) from the depart 9 of ure 16 to decide to tanker all the fuel necessary for the return flight (B-A) from the departure airport A. airport A. Figure 6. Example for a 600 NM flight performing a full (100%) tankering. Figure 6. Figure 6. Example for a Example for a 600 600 NM flight perf NM flight performing orming a full (10 a full (100%) 0%) tankering. tankering. However, above 600 NM, it is no longer possible for this aircraft model to do full However, above 600 NM, it is no longer possible for this aircraft model to do full However, above 600 NM, it is no longer possible for this aircraft model to do full tankering, only partial tankering could be envisaged. tankering, only partial tankering could be envisaged. tankering, only partial tankering could be envisaged. Let us take the example of a 900 NM flight with the same aircraft model as before, Let us take the example of a 900 NM flight with the same aircraft model as before, Let us take the example of a 900 NM flight with the same aircraft model as before, same empty operating weight of 43.7 tonnes, same payload of 17.6 tonnes, same maximum same empty operating weight of 43.7 tonnes, same payload of 17.6 tonnes, same maximum same empty operating weight of 43.7 tonnes, same payload of 17.6 tonnes, same maximum fuel load capacity of 23.5 tonnes of fuel, and same maximum take-off weight of 77 tonnes. fuel load capacity of 23.5 tonnes of fuel, and same maximum take-off weight of 77 tonnes. fuel load capacity of 23.5 tonnes of fuel, and same maximum take-off weight of 77 tonnes. It wi It will ll need 6.4 tonnes of need 6.4 tonnes of fuel fuel to perf to perform orm thi this flight, s flight, consi consisting sting of 5 of 5.2 tonnes .2 tonnes f for the or trip the and trip It will need 6.4 tonnes of fuel to perform this flight, consisting of 5.2 tonnes for the trip and 1.2 tonnes o 1.2 tonnes of reserve. f reserv When e. When not not doing do tankering ing tankering ( (Figur Figure 7 e 7), the ), t fuel he fconsumption uel consumptof ion of this and 1.2 tonnes of reserve. When not doing tankering (Figure 7), the fuel consumption of tair his a craft ircr model aft model over t over this distance his distanc is now e is now 5 5.19 tonnes. .19 tonnes. On On arrival arat riva airport l at aiB, rport ther B, there is e is 1 tonne 1 this aircraft model over this distance is now 5.19 tonnes. On arrival at airport B, there is 1 tonne of re of reserve fuel serve fuel le left, and ft, theand the total total weight weig of the ht of the aircraft aircr doesa not ft doe exceed s not exceed 66 tonnes 66 tonnes certified tonne of reserve fuel left, and the total weight of the aircraft does not exceed 66 tonnes cert maximum ified ma landing ximum weight landing for weight a safe for a sa landing. fe landing. certified maximum landing weight for a safe landing. Figure 7. Example for a 900 NM flight with no tankering. Figure 7. Example for a 900 NM flight with no tankering. Figure 7. Example for a 900 NM flight with no tankering. Under the same operational assumptions mentioned above, this type of aircraft can- Under the same operational assumptions mentioned above, this type of aircraft can- Under the same operational assumptions mentioned above, this type of aircraft cannot not do 100% fuel tankering on a 900 NM flight but only a maximum of 50%, otherwise it not do do 100% 100% fuel ftankering uel tankerin ong a on 900aNM 900 flight NM fbut light only buta on maximum ly a maxim of u 50%, m ofotherwise 50%, othe it rwise would it would exceed its authorized landing weight at airport B. At 50% fuel tankering (Figure 8), would exceed excee its authorized d its authori landing zed land weight ing wat eight airport at airp B. o At rt 50% B. Atfuel 50%tankering fuel tanke (Figur ring (Figure 8) e 8), this , this flight burns 3.66% more fuel than if it had not carried that “extra” fuel. Consequently, flight burns 3.66% more fuel than if it had not carried that “extra” fuel. Consequently, if this flight burns 3.66% more fuel than if it had not carried that “extra” fuel. Consequently, if the fuel price negotiated by its airline operator at the destination airport B is 3.66% more the fuel price negotiated by its airline operator at the destination airport B is 3.66% more if the fuel price negotiated by its airline operator at the destination airport B is 3.66% more expensive than at the departure airport A, it might be worthwhile for this operator, from expensi expensive ve than a than att the the departur departure e ai arport irport A, A, itit might might be worthwhi be worthwhile lfor e for thi this operator s operat,or, from from an Aerospace 2021, 8, x FOR PEER REVIEW 10 of 16 an economic point of view, to decide to tanker 50% of the fuel necessary for the return economic point of view, to decide to tanker 50% of the fuel necessary for the return flight an economic point of view, to decide to tanker 50% of the fuel necessary for the return flight (B-A) from the departure airport A. (B-A) from the departure airport A. flight (B-A) from the departure airport A. Figure 8. Example for a 900 NM flight performing a 50% partial fuel tankering. Figure 8. Example for a 900 NM flight performing a 50% partial fuel tankering. 4.7. STEP 3: Calculate the Number of Flights for Which Full or Partial Tankering Is Operationally Possible After having determined the tankering capability for each aircraft model, it is neces- sary to estimate how many aircraft of the same model operated in ECAC could potentially do tankering and at what percentage level. This is illustrated in Figure 9, which shows for one specific aircraft model the percentage of fuel tankering possible as a function of the flight distance in NM and the percentage of additional fuel burnt. Figure 9. % of extra fuel burn as a function of % of tankering and distance flown for a specific aircraft model. Once the percentage of tankering capacity for this aircraft model for several theoret- ical distance flown are obtained, they have been applied to the real traffic in ECAC grouped by distance flown as illustrated in Figure 10. Figure 10. % of flight and % of feasible tankering per distance. Aerospace 2021, 8, x FOR PEER REVIEW 10 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 10 of 16 Aerospace 2021, 8, 37 10 of 16 Figure 8. Example for a 900 NM flight performing a 50% partial fuel tankering. Figure 8. Example for a 900 NM flight performing a 50% partial fuel tankering. 4.7. STEP 3: Calculate the Number of Flights for Which Full or Partial Tankering Is 4.7. STEP 3: Calculate the Number of Flights for Which Full or Partial Tankering Is 4.7. STEP 3: Calculate the Number of Flights for Which Full or Partial Tankering Is Operationally Possible Operationally Possible Operationally Possible After having determined the tankering capability for each aircraft model, it is necessary After having determined the tankering capability for each aircraft model, it is neces- After having determined the tankering capability for each aircraft model, it is neces- to estimate how many aircraft of the same model operated in ECAC could potentially do sary to estimate how many aircraft of the same model operated in ECAC could potentially sary to estimate how many aircraft of the same model operated in ECAC could potentially tankering and at what percentage level. This is illustrated in Figure 9, which shows for one do tankering and at what percentage level. This is illustrated in Figure 9, which shows for do tankering and at what percentage level. This is illustrated in Figure 9, which shows for specific aircraft model the percentage of fuel tankering possible as a function of the flight one specific aircraft model the percentage of fuel tankering possible as a function of the one specific aircraft model the percentage of fuel tankering possible as a function of the distance in NM and the percentage of additional fuel burnt. flight distance in NM and the percentage of additional fuel burnt. flight distance in NM and the percentage of additional fuel burnt. Figure 9. % of extra fuel burn as a function of % of tankering and distance flown for a specific aircraft Figure 9. % of extra fuel burn as a function of % of tankering and distance flown for a specific Figure 9. % of extra fuel burn as a function of % of tankering and distance flown for a specific aircraft model. mod aircraft el. model. Once the percentage of tankering capacity for this aircraft model for several theoret- Once the percentage of tankering capacity for this aircraft model for several theoretical Once the percentage of tankering capacity for this aircraft model for several theoret- ical distance flown are obtained, they have been applied to the real traffic in ECAC distance flown are obtained, they have been applied to the real traffic in ECAC grouped by ical distance flown are obtained, they have been applied to the real traffic in ECAC grouped by distance flown as illustrated in Figure 10. distance flown as illustrated in Figure 10. grouped by distance flown as illustrated in Figure 10. Figure Figure 10. 10. % % of of flight and % of flight and % of feasible feasible tankering per distance. tankering per distance. Figure 10. % of flight and % of feasible tankering per distance. 4.8. STEP 4: Estimate the Economic Opportunity of Tankering The fact that it is “technically possible” for a flight to make a full or partial tankering, does not mean that the airline operating that aircraft will decide to do so. Putting aside safety and special considerations at the destination airport (B), it was assumed in our model that this decision will be based on the cost savings that can be made, thanks to the difference in fuel prices negotiated at airports A and B. As can be seen in Figure 11, the average worldwide price of jet fuel is not constant. It is largely influenced by the crude oil price. Aerospace 2021, 8, x FOR PEER REVIEW 11 of 16 4.8. STEP 4: Estimate the Economic Opportunity of Tankering The fact that it is “technically possible” for a flight to make a full or partial tankering, does not mean that the airline operating that aircraft will decide to do so. Putting aside safety and special considerations at the destination airport (B), it was assumed in our model that this decision will be based on the cost savings that can be made, thanks to the difference in fuel prices negotiated at airports A and B. Aerospace 2021, 8, 37 11 of 16 As can be seen in Figure 11, the average worldwide price of jet fuel is not constant. It is largely influenced by the crude oil price. Figure 11. Average world price of crude Oil and Jet Fuel (IATA index Platts; https://www.iata.org/en/publications/eco- Figure 11. Average world price of crude Oil and Jet Fuel (IATA index Platts; https://www.iata.org/en/publications/ nomics/fuel-monitor/). economics/fuel-monitor/). In addition, the following factors influence also the price of jet fuel in each airport: In addition, the following factors influence also the price of jet fuel in each airport: ● Country; Country; ● Taxes (Fuel taxes in some ECAC country only for domestic flights), and refining costs; Taxes (Fuel taxes in some ECAC country only for domestic flights), and refining costs; ● Negotiation period; Negotiation period; ● Profit, quantities, and supply competition at airports; Profit, quantities, and supply competition at airports; ● Distribution technique; Distribution technique; ● Purchasing power and size of the aircraft operator’s fleet. Purchasing power and size of the aircraft operator ’s fleet. Generally, each airline negotiates, with a fuel provider, a fuel price at each airport it Generally, each airline negotiates, with a fuel provider, a fuel price at each airport it serves for an agreed duration. serves for an agreed duration. In addition, most airlines protect themselves against major fluctuations in fuel prices In addition, most airlines protect themselves against major fluctuations in fuel prices for the next six months to two years by using various hedging strategies and instruments. for the next six months to two years by using various hedging strategies and instruments. However However, , “h “hedging” edging” h has as no no s significant ignificant ef effect fect on on ex existing isting fuel pr fuel price ice d dififer fference encess between between airports, airports, and and could could only only m mar arg ginally inally red reduce uce the benef the benefit it of of tankering tankering [1 [133,14 ,14].]. Airlines Airlines ne negotiated gotiated ffuel uel pri prices ces are ar comm e commer ercial cially ly sens sensitive itive datdata a and and must must rema remain in con- confidential. fidential. For For this r this eason, the values reason, the values presented on presented the on map the (Figur map (Figur e 12) are e 12 aver ) arag e averaged ed values values calculated from the fuel prices negotiated by the airlines for which we were able to calculated from the fuel prices negotiated by the airlines for which we were able to obtain obtain this information. Nevertheless, it shows that there are large differences between fuel this information. Nevertheless, it shows that there are large differences between fuel prices at airports, e.g., Fuel price at Amsterdam (purple dot, so 0%) is among the cheapest prices at airports, e.g., Fuel price at Amsterdam (purple dot, so 0%) is among the cheapest in Europe. Fuel price at Ibiza and Hamburg or Oslo (yellow dots) is 30% more expensive in Europe. Fuel price at Ibiza and Hamburg or Oslo (yellow dots) is 30% more expensive than the cheapest airports, such as Amsterdam. Fuel price at Heathrow (light cyan dot) is than the cheapest airports, such as Amsterdam. Fuel price at Heathrow (light cyan dot) is 20%more expensive than the cheapest airports, such as Amsterdam, but 20% cheaper than Glasgow (red dot, 40%). In this study, we considered that each tonne of CO emitted required the purchase of CO allowances, which, as explained in STEP 1, is not the case. This cost is deducted from the benefit of doing tankering. Aerospace 2021, 8, x FOR PEER REVIEW 12 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 12 of 16 20%more expensive than the cheapest airports, such as Amsterdam, but 20% cheaper than Glasgow (red dot, 40%). Aerospace 2021, 8, 37 20%more expensive than the cheapest airports, such as Amsterdam, but 20% cheaper than 12 of 16 Glasgow (red dot, 40%). Figure 12. Illustrative fuel price difference at airports. In this study, we considered that each tonne of CO2 emitted required the purchase of CO2 allow Figure 12. ances, wh Illustrative fu ich, as expla el pric ined e diff in erence at STEP 1, airports. is not the case. This cost is deducted from Figure 12. Illustrative fuel price difference at airports. the benefit of doing tankering. In this study, we considered that each tonne of CO2 emitted required the purchase of Figure 13 shows the net savings that could be achieved according to different percent- Figure 13 shows the net savings that could be achieved according to different percent- CO ages 2 allow of fuel anc tankering es, which, and as dif expla ferent ined fuel in price STEP for 1, is a not 600 t NM he cflight. ase. Thi Itsmust cost is be ded noted ucted from that this ages of fuel tankering and different fuel price for a 600 NM flight. It must be noted that the benefit o figure is simplified f doing t while anker in ing. the real processing there was a 10% step for every partial fuel this figure is simplified while in the real processing there was a 10% step for every partial tankering and real fuel price difference from some airlines. In the figure, it can be seen that Figure 13 shows the net savings that could be achieved according to different percent- fuel tankering and real fuel price difference from some airlines. In the figure, it can be seen age theseconomic of fuel tanker advant ingage and of di fuel fferent tankering fuel price is not foralways a 600 N possible. M flight.For It must differ be ences notein d t fuel hat that the economic advantage of fuel tankering is not always possible. For differences in tprices his figbetween ure is simpli airports fied whi (A and le inB) thof e re 2al and processin 5% theg benefi there was ts do a not 10% step for reach the 30 ev ery partial threshold. fuel prices between airports (A and B) of 2 and 5% the benefits do not reach the 30€ thresh- For a fuel price difference of 10% and for tankering from 40 to 100% the cost savings range fuel tankering and real fuel price difference from some airlines. In the figure, it can be seen old. For a fuel price difference of 10% and for tankering from 40 to 100% the cost savings from 44.4 to 94.9 . At a fuel price difference of 20% and tankering from 20 to 100% the cost that the economic advantage of fuel tankering is not always possible. For differences in range from 44.4 to 94.9€. At a fuel price difference of 20% and tankering from 20 to 100% savings range from 66.5 to 292.5 . fuel prices between airports (A and B) of 2 and 5% the benefits do not reach the 30€ thresh- the cost savings range from 66.5 to 292.5€. old. For a fuel price difference of 10% and for tankering from 40 to 100% the cost savings range from 44.4 to 94.9€. At a fuel price difference of 20% and tankering from 20 to 100% the cost savings range from 66.5 to 292.5€. Figure 13. Net saving and airport fuel price difference vs % of fuel tankering for a 600 NM flight. Figure 13. Net saving and airport fuel price difference vs % of fuel tankering for a 600 NM flight. Finally, by applying the Steps 2, 3, and 4 described above to all ECAC flights and Figure 13. Net saving and airport fuel price difference vs % of fuel tankering for a 600 NM flight. aircraft models considered in the simulations, the following results were obtained: As indicated in the Table 1 fuel tankering could result in a net saving of 265 M  per year for the airlines, but would generate 286,000 additional tonnes of fuel burnt (equivalent Aerospace 2021, 8, x FOR PEER REVIEW 14 of 17 Finally, by applying the Steps 2, 3, and 4 described above to all ECAC flights and aircraft models considered in the simulations, the following results were obtained: Table 1. Evaluated Net savings due to tankering versus Extra CO2 emitted. Aerospace 2021, 8, 37 13 of 16 Extra fuel burnt Cost to transport Extra CO2 Cost of purchasing Net saving = Tankering (tonnes/year) extra fuel emitted CO2 allowances saving - [Extra fuel + CO2 to 0.54% of ECAC jet fuel used) and 901,000 tonnes of CO emissions in the ECAC area (M€/year) (tonnes/year) (M€/year) cost] (M€/year) per year. Table 1. Evaluated Net savings due to tankering versus Extra CO emitted. Full tankering 160,000 88 504,000 10 217 Net Saving = Cost of Cost to Transport Extra CO Tankering Saving Partial tankering 126,000 69 397,000 8 48 Extra Fuel Burnt Purchasing CO Extra Fuel Emitted [Extra Fuel + (tonnes/year) Allowances (M /year) (tonnes/year) CO Cost] (M /year) (M /year) Total tankering 286,000 157 901,000 18 265 Full tankering 160,000 88 504,000 10 217 As indicated in the Table 1 fuel tankering could result in a net saving of 265 M€ per Partial tankering 126,000 69 397,000 8 48 year for the airlines, but would generate 286,000 additional tonnes of fuel burnt (equiva- Total tankering 286,000 157 901,000 18 265 lent to 0.54% of ECAC jet fuel used) and 901,000 tonnes of CO2 emissions in the ECAC area per year. Figure 14 shows that on the short and medium-haul fleet, the percentage of flights that Figure 14 shows that on the short and medium-haul fleet, the percentage of flights that could perform full fuel tankering decreases with the distance to be flown. This is mainly could perform full fuel tankering decreases with the distance to be flown. This is mainly due to the fact that as the distance to be flown increases, the aircraft has to carry much more due to the fact that as the distance to be flown increases, the aircraft has to carry much fuel from the departure airport (Airport A), therefore increasing its landing weight at the more fuel from the departure airport (Airport A), therefore increasing its landing weight destination airport (Airport B). When this landing weight exceeds the certified Maximum at the destination airport (Airport B). When this landing weight exceeds the certified Max- Landing Weight, full fuel tankering is not possible anymore. Partial tankering in turn takes imum Landing Weight, full fuel tankering is not possible anymore. Partial tankering in over until itself reaches its operational limit, for the same reasons, at more than 1500 NM. turn takes over until itself reaches its operational limit, for the same reasons, at more than Besides, it is obvious that the difference in fuel price has also a certain influence. 1500 NM. Besides, it is obvious that the difference in fuel price has also a certain influence. Figure 14. % of flights which could exercise fuel tankering (and save money by doing so), per distance flown. Figure 14. % of flights which could exercise fuel tankering (and save money by doing so), per distance flown. Figure 15 shows that distance matters, the longer the distance to be covered, the more Figure 15 shows that distance matters, the longer the distance to be covered, the more fuel needs to be tankered, leading to an increase in extra fuel burn. It should be noted that fuel needs to be tankered, leading to an increase in extra fuel burn. It should be noted that doubling the distance travelled results in more than doubling the fuel needed to carry this doubling the distance travelled results in more than doubling the fuel needed to carry this extra extra fuel fuel, , a and nd thus the resul thus the resulting ting emissions. emissions. Figure 16 shows the distribution of the 160,000 tonnes of additional fuel burnt (505,000 tonnes of CO ) due to full fuel tankering and the 126,000 tonnes of additional fuel burnt (397,000 tonnes of CO ) due to partial tankering per distance flown. It clearly shows that the partial tankering is mainly performed over long distances in ECAC and represents a significant part of the extra fuel burnt. Although only 4.5% of flights perform partial tankering, they account for nearly half of the CO emissions (44%) due to this practice. 2 Aerospace 2021, 8, x FOR PEER REVIEW 15 of 17 Aerospace 2021, 8, x FOR PEER REVIEW 15 of 17 Aerospace 2021, 8, 37 14 of 16 Figure 15. Extra fuel burn per distance flown. Figure 16 shows the distribution of the 160,000 tonnes of additional fuel burnt (505,000 tonnes of CO2) due to full fuel tankering and the 126,000 tonnes of additional fuel burnt (397,000 tonnes of CO2) due to partial tankering per distance flown. It clearly shows that the partial tankering is mainly performed over long distances in ECAC and represents a significant part of the extra fuel burnt. Although only 4.5% of flights perform partial Figure 15. Extra fuel burn per distance flown. Figure 15. Extra fuel burn per distance flown. tankering, they account for nearly half of the CO2 emissions (44%) due to this practice. Figure 16 shows the distribution of the 160,000 tonnes of additional fuel burnt (505,000 tonnes of CO2) due to full fuel tankering and the 126,000 tonnes of additional fuel burnt (397,000 tonnes of CO2) due to partial tankering per distance flown. It clearly shows that the partial tankering is mainly performed over long distances in ECAC and represents a significant part of the extra fuel burnt. Although only 4.5% of flights perform partial tankering, they account for nearly half of the CO2 emissions (44%) due to this practice. Figure 16. Tonnes of extra fuel burn per distance flown. Figure 16. Tonnes of extra fuel burn per distance flown. 5. Conclusions 5. Conclusions As aviation is a very competitive market, airlines must do everything possible to As aviation is a very competitive market, airlines must do everything possible to minimize their operating costs, in particular regarding fuel cost, which represents 17 to minimize their operating costs, in particular regarding fuel cost, which represents 17 to 25% of their operating expenses [1]; this goes even up to 50% for some low-cost carriers. 25% of their operating expenses [1]; this goes even up to 50% for some low-cost carriers. Figure 16. Tonnes of extra fuel burn per distance flown. Consequently, airlines are using tools for identifying the value of performing fuel tanker- Consequently, airlines are using tools for identifying the value of performing fuel tankering, ing, a practice whereby an aircraft carries more fuel than required for its flight in order to a practice whereby an aircraft carries more fuel than required for its flight in order to save 5. Conclusions save costs. However, fuel tankering is not without environmental consequences, as the costs. However, fuel tankering is not without environmental consequences, as the more more fuel an aircraft carries, the more fuel it burns and the more CO2 it emits. The use of As aviation is a very competitive market, airlines must do everything possible to fuel an aircraft carries, the more fuel it burns and the more CO it emits. The use of fuel minimize their operating costs, in particular regarding fuel cost, which represents 17 to tankering by long-haul flights will be the subject of a future study. This study is limited to 25% of their operating expenses [1]; this goes even up to 50% for some low-cost carriers. flights up to 1500 and 2500 NM, corresponding mainly to short and medium-haul flights. Consequently, airlines are using tools for identifying the value of performing fuel tanker- It is estimated that fuel tankering could result in a net saving of 265 M  per year for the ing, a practice whereby an aircraft carries more fuel than required for its flight in order to airlines, but would generate 286,000 additional tonnes of fuel burnt (equivalent to 0.54% of save costs. However, fuel tankering is not without environmental consequences, as the ECAC jet fuel used) and 901,000 tonnes of CO emissions in the ECAC area per year. This is more fuel an aircraft carries, the more fuel it burns and the more CO2 it emits. The use of equivalent to about 2800 round-trips between Paris and New York or the annual emissions Aerospace 2021, 8, 37 15 of 16 of a European city of 100,000 inhabitants. This is a substantial economic benefit but also a significant environmental impact. Consequently, fuel tankering could offset the benefit of initiatives to save fuel and reduce aviation CO emissions. At a time when aviation is challenged for its contribution to climate change, a practice, such as fuel tankering, that generates significant additional CO emissions is questionable. Unfortunately, the COVID19 crisis has created such economic pressure that airlines have intensified the practice of fuel tankering since then, as reported by some pilots. Author Contributions: All the authors contributed equally to this work. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data used to produce this analysis are EUROCONTROL data and are not available in the public domain. In particular, negotiated fuel prices at the airports used in this study remain confidential. Acknowledgments: This study was carried out with the aim of raising awareness of the considerable environmental impact of a practice such as fuel tankering. It was carried out independently, but required the collection of commercially sensitive information, which we had to anonymize. The results of this study were published in EUROCONTROL’s first “Think Paper”, and subsequently picked up in many newspapers, news feeds and other media [15,16]. Following its publication, a number of airlines had begun to reflect on reducing or even abandoning this economic practice. The authors would like to express their deep gratitude to all colleagues who were directly or indirectly involved in this study, and to the EUROCONTROL top management who had the courage to make it public. Conflicts of Interest: There are no conflicts of interest whatsoever. References 1. Kumar, N.; Frolik, P.; Joshi, G.; Ramadugu, H. World Air Transport Statistics; IATA: Montreal, QC, Canada, 2017. 2. ICAO. Operational Opportunities to Reduce Fuel Burn and Emissions, 1st ed.; Doc 10013; ICAO: Montreal, QC, Canada, 2014. 3. Filippone, A. Case Study Fuel Tankering: Is It Worth It? The University of Manchester, February 2015. Available online: http: //www.flight.mace.manchester.ac.uk/aircraft-performance-software/case-studies/by-solution/11_CS_Fuel_Tankering.pdf (ac- cessed on 30 January 2021). 4. Lindgren, M.; Brynhagen, M. Fuel Tankering. Master ’s Thesis, Lund University School of Engineering at Campus Helsing- borg, Helsingborg, Sweden, 2012. Available online: https://www.iea.lth.se/publications/BS-Theses/Full%20document/3018 _Brynhagen_Lindgren.pdf (accessed on 30 January 2021). 5. Lesinski, J.W., III. Tankering Fuel: A Cost Saving Initiative. Graduate Research Paper, Department of the Air Force at Air Force Institute of Technology, Wright-Patterson Air Force Base, Ohio, May 2011. Available online: https://apps.dtic.mil/dtic/tr/ fulltext/u2/a547625.pdf (accessed on 8 October 2020). 6. Tavares Guerreiro, J.A.; Muller, C.; Fibeiro Correira, A. A fuel tankering model applied to a domestic airline network. J. Adv. Transp. 2013, 47, 386–398. [CrossRef] 7. Focus on Fuel Part Three: Global Fuel Pricing and Availability. Retrieved March 2019. Available online: https://www.jetex.com/ global-fuel-pricing-and-availability/ (accessed on 8 October 2020). 8. Thurber, M. Tankering Benefits Tangible and Achievable. October 2015, Retrieved March 2019. Available online: https:// www.ainonline.com/aviation-news/business-aviation/2015-10-12/tankeringbe-ne_ts-tangible-and-achievable (accessed on 8 October 2020). 9. Benito Ruiz de Villa, A. Práctica de tankering en las líneas aéreas españolas. In Proceedings of the IX Congreso de Ingeniería del Transporte, CIT2010, Madrid, Spain, 7–9 July 2010; Available online: http://oa.upm.es/9544/ (accessed on 8 October 2020). 10. EASA (European Aviation Safety Agency); EEA (European Environment Agency); EUROCONTROL. European Aviation Envi- ronmental Report 2019. Available online: https://ec.europa.eu/transport/sites/transport/files/2019-aviation-environmental- report.pdf (accessed on 8 October 2020). [CrossRef] 11. Methods and Apparatus for Providing Fuel Tankering Data Onboard and Aircraft. Pub. No. US 2018/0189704 A1, July 2018. Available online: https://www.freepatentsonline.com/y2018/0189704.html (accessed on 8 October 2020). 12. Daley, B.; Preston, H. Aviation and climate change: Assessment of policy options. In Climate Change and Aviation. Issues, Challenges and Solutions; Gössling, S., Upham, P., Eds.; Earthscan: London, UK, 2009; pp. 347–372. Aerospace 2021, 8, 37 16 of 16 13. Morell, P.; Swan, W. Airline Jet Fuel Hedging: Theory and Practice. 24 November 2006. Available online: https://www. researchgate.net/publication/228628896_Airline_Jet_Fuel_Hedging_Theory_and_Practicel (accessed on 8 October 2020). [Cross- Ref] 14. Bloomberg Markets and Finance. Ryanair ’s O’Leary Says Happy to Continue as CEO for 2 to 3 Years. Available online: https: //www.youtube.com/watch?v=PgpwYeEj5Roat0\T1\textquoteright57\T1\textquotedblright (accessed on 8 October 2020). 15. BBC Panorama. Can Flying Go Green? Available online: https://www.youtube.com/watch?v=mPhOS4uXkmM (accessed on 8 October 2020). 16. Rowlatt, J. Climate change: British Airways Reviews ‘Fuel-Tankering’ over Climate Concerns. BBC News. 11 November 2019. Available online: https://www.bbc.com/news/science-environment-50365362 (accessed on 8 October 2020). http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aerospace Multidisciplinary Digital Publishing Institute

Fuel Tankering: Economic Benefits and Environmental Impact for Flights Up to 1500 NM (Full Tankering) and 2500 NM (Partial Tankering)

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aerospace Article Fuel Tankering: Economic Benefits and Environmental Impact for Flights Up to 1500 NM (Full Tankering) and 2500 NM (Partial Tankering) , † † † † † Laurent Tabernier * , Esther Calvo Fernández , Andreas Tautz , Robin Deransy and Peter Martin European Organisation for the Safety of Air Navigation—EUROCONTROL, 91220 Brétigny/Orge, France; esther.calvo-fernandez@eurocontrol.int (E.C.F.); andreas.tautz@eurocontrol.int (A.T.); robin.deransy@eurocontrol.int (R.D.); peter.martin@eurocontrol.int (P.M.) * Correspondence: laurent.tabernier@eurocontrol.int † Authors contributed equally to this work. Abstract: The majority of emissions from aviation come from the combustion of the fuel required to operate each flight. Keeping the fuel consumption required for a safe flight to the absolute minimum is therefore the simplest and most effective way to ensure that emissions from that flight are kept to a minimum. In practice, however, the fuel load is determined by each aircraft operator on the basis of a number of criteria maximizing first cost efficiency, rather than fuel savings. In this context, tankering is the practice of carrying more fuel than is necessary for the safe execution of the flight to avoid or minimize refueling at the destination airport. It offers an economic advantage when there is a significant difference in fuel prices between the departure and arrival airports, but considerably increases the amount of emissions produced, because the more fuel an aircraft carries, the heavier it is, and carrying this extra weight increases its fuel consumption. This paper presents the steps followed by EUROCONTROL in conducting a first study to estimate the number of times this practice would Citation: Tabernier, L.; Fernández, offer an economic benefit and the amount of extra CO emissions that would result. This study, E.C.; Tautz, A.; Deransy, R.; Martin, P. limited to flights up to 1500 and 2500 NM, corresponding mainly to short and medium-haul flights, Fuel Tankering: Economic Benefits estimates that, in 2018, 21% of ECAC (In this paper, ECAC refers to the geographical region defined and Environmental Impact for Flights by the 44 member states that signed the European Civil Aviation Conference) flights would perform Up to 1500 NM (Full Tankering) and fuel tankering beneficially. This would represent a net saving of 265 M  per year for the airlines, 2500 NM (Partial Tankering). but the burning of 286,000 tonnes of additional fuel (equivalent to 0.54% of ECAC jet fuel used), or Aerospace 2021, 8, 37. https:// 901,000 tonnes of CO per year. At a time when aviation is challenged for its contribution to climate doi.org/10.3390/aerospace8020037 change, the use of fuel tankering for economic reasons is therefore highly questionable. Academic Editor: David Raper Received: 14 December 2020 Keywords: fuel tankering; CO emissions; economic benefit; fuel price Accepted: 26 January 2021 Published: 31 January 2021 Publisher’s Note: MDPI stays neutral 1. Introduction with regard to jurisdictional claims in As aviation is a highly competitive market, airlines must do everything possible to published maps and institutional affil- minimize their operating costs, in particular regarding fuel cost, which account for 17 to iations. 25% of their operating expenses [1]; this goes even up to 50% for some low-cost carriers. Furthermore, as the majority of aviation emissions come from the combustion of the fuel needed to operate each flight, it would seem logical that keeping the fuel consumption required for each flight to the absolute safe minimum is the simplest and most effective way Copyright: © 2021 by the authors. to ensure that both the emissions from that flight and the total cost of the fuel embarked Licensee MDPI, Basel, Switzerland. are minimized. This would mean carrying as little fuel as possible for the safe execution of This article is an open access article each flight. This is not the case. distributed under the terms and In practice, safety and special considerations at the destination airport aside, the fuel conditions of the Creative Commons load is determined by each aircraft operator according to a number of criteria that maximize Attribution (CC BY) license (https:// cost savings rather than fuel savings. creativecommons.org/licenses/by/ Fuel tankering is a practice used in this context. 4.0/). Aerospace 2021, 8, 37. https://doi.org/10.3390/aerospace8020037 https://www.mdpi.com/journal/aerospace Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 In practice, safety and special considerations at the destination airport aside, the fuel Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 load In p is de ract term ice, ined b safety y e and sp ach aircr ecia al con ft opserat ider or acco ations at rdi tn hg t e d oe a num stination ber of crit airport as eriide, a th t at h m e fu ax- el Aerospace 2021, 8, x FOR PEER REVIEW 2 of 16 load In p is de ract term ice, ined b safety y e and sp ach aircr ecia al con ft opserat ider or acco ations at rdi tn hg t e d oe a num stination ber of crit airport as eriide, a th t at h m e fu ax- el imize cost savings rather than fuel savings. Aerospace 2021, 8, 37 2 of 16 imize load In p is d cost savings rather e ract term ice, ined b safety y e and sp a c than fue h aircr ecia al con lft s op avings. serat ider or acco at ions at rdi tn hg t e d oe a num stination ber of crit airport as eriide, a th t at h m e fu ax- el Fuel tankering is a practice used in this context. In practice, safety and special considerations at the destination airport aside, the fuel imize load Fuel ta is d cost savings rather etenkeri rmined b ng is ya e pra a c than fue hc aircr tice used i alft s op avings. n erat thior acco s context. rdin g to a number of criteria that max- 2. Wh imize load 2. What In p is d at Is cost savings rather Is e ract te Fu Fuel rm ice, el ined b s T Tankering a afet nky y er e and sp ing a c than fue h aircr ecia al con lft s op avings. serat ider or acco at ions at rdi tn hg t e d oe a num stination ber of crit airport as eriide, a th t at h m e fu ax- el Fuel tankering is a practice used in this context. 2. Wh imize load Fuel ta is d at Is cost savings rather ete Fu nkeri rm el ined b T n ag is nky er a e pra ing a c than fue h c aircr tice used i alft s op avings. n erat thior acco s context. rdin g to a number of criteria that max- Fuel tan Fuel tankering kering is is a pr a practice actice whereby whereby an an aircr aircraft aft c carries arries more fuel than required more fuel than required for for its its 2. Wh imize Fuel ta at Is cost savings rather Fu nkeri el T n ag is nker a pra ing than fue ctice used i l savings. n this context. safe flight in order to reduce or avoid refueling at the destination airport [2]. safe fl Fuel tan ight in k order t ering is o re a pr du actice ce or avoid whereby refue an ling aircr at a t ft c hea dest rries in more fuel than required ation airport. [2] for its 2. Wh Fuel ta at Is Fu nkeri el T n ag is nker a pra ing ctice used in this context. Fuel tan Fuel tankering kering is can a pr be actice donewhereby for two reasons: an aircraft carries more fuel than required for its safe fl Fuel tank ight in order t ering can o re be done duce or avoid for two refue reaso ling ns: at the destination airport. [2] 2. What Is Fuel Tankering safe fl Fuel tank Fuel tan ight in k order t erin ering is g can o re a pr be done du actice ce or avoid for two whereby refue reaso an ling aircr ns: at a t ft c hea dest rries in more fuel than required ation airport. [2] for its When it is operationally not possible or desirable to refuel at the destination airport, ● When it is operationally not possible or desirable to refuel at the destination airport, 2. What Is Fuel Tankering Fuel tankering is a practice whereby an aircraft carries more fuel than required for its safe fl Fuel tank ight in order t ering can o re be done duce or avoid for two refue reaso ling ns: at the destination airport. [2] due to circumstances, such as the following: ● When due to c it is op ircum eration stances a,lly su no ch t possib as the fo le or llow die ng: sira ble to refuel at the destination airport, safe fl Fuel tank Fuel tan ight in k order t erin ering is g can o re a pr be done du actice ce or avoid for two whereby refue reaso an ling aircr ns: at a t ft c hea dest rries in more fuel than required ation airport. [2] for its ● When due to c it is op ircum eration stances a,lly su no ch t possib as the fo le or llow die ng: sira ble to refuel at the destination airport, social disruption;  social disruption; safe fl Fuel tank ight in order t ering can o re be done duce or avoid for two refue reaso ling ns: at the destination airport. [2] ● When it is operationally not possible or desirable to refuel at the destination airport, due to circumstances, such as the following: technical failures of the refueling installation;  s te ochnica cial disru l fail pures tion; of t he refueling installation; Fuel tankering can be done for two reasons: ● When due to c it is op ircum eration stances a,lly su no ch t possib as the fo le or llow die ng: sira ble to refuel at the destination airport, fuel shortages;  social disruption;  t fue echnica l shor l f tage ailures s; of the refueling installation; ● When it is operationally not possible or desirable to refuel at the destination airport, due to circumstances, such as the following: contaminated fuel at destination airport;  s t fue e ochnica cia l sho l dir sru l f tage ail pures ti s; on; of t he refueling installation;  contaminated fuel at destination airport; due to circumstances, such as the following: very short turnaround times;  social disruption;  t fue cont echnica l sho aminat r l f tage aed ilures s; fu el of t at de he ref stin u at elion ing airp insto ar llta ; tion;  very short turnaround times; risks of delays.  s te ochnica cial disru l fail pures tion; of t he refueling installation;  fue cont very short turna risk ls o sho am f de inat rtage lay ed s; s fu . r el ound ti at dest mes; ination airport;  t fue cont echnica l sho aminat r l f tage aed ilures s; fu el of t at de he ref stin u at elion ing airp insto ar llta ; tion;  T o achieve very short turna risks ofsavings delays. when round ti themes; cost of fuel and associated services at the departure ● To achieve savings when the cost of fuel and associated services at the departure  airport fue cont very short turna risk is ls o sho am significantly f de inat rtage lay ed s; s fu . r el ound ti lower at dest than mes; inatat ion the airp destination ort; airport. ● airp To ach orti eve is si savings when gnificantly lowe the cost r than at of th fue e dest l and in at assoc ion ai iated service rport. s at the departure  cont very short turna risks o am f de inat lay eds fu . r el ound ti at dest mes; ination airport; ● To ach There ar ieve e two savings when types of fuel the cost tankering: of fuel and associated services at the departure airport is significantly lower than at the destination airport. There are two types of fuel tankering:  very short turnaround times;  risks of delays. ● airp To ach orti eve is si savings when gnificantly lowe the cost r than at of th fue e dest l and in at assoc ion ai iated service rport. s at the departure There are two Full (fuel) tankering, types owhich f fuel tankerin consistsg: in transporting all the fuel needed for the return ● Full (fuel) tankering, which consists in transporting all the fuel needed for the return  risks of delays. ● To achieve savings when the cost of fuel and associated services at the departure airport is significantly lower than at the destination airport. flight from the departure airport to avoid refueling at the destination airport, and There are two types of fuel tankering: ● f Ful light f l (fue rom l) t the departure ankering, which ai cons rport to a ists in v t oid refuel ransportiing al ng at l the fuel the desti needed f nation ai orport, r the return and ● airp To ach orti eve is si savings when gnificantly lowe the cost r than at of th fue e dest l and in at assoc ion ai iated service rport. s at the departure There are two Partial (fuel) tankering, types of fue which l tankerin consists g: in transporting only part of the fuel needed for ●● Pa f Ful light f rtia l (fue l r(om fl) u t e the departure a l) n t k aering nkeri,n wh g, whi ich ai cons rport to a ch consi ists in sv ts in t oid refuel rantsporti ransping al o nr g a tint l the fuel g the desti only pa needed f r nta o tion ai f theo frport, r the return uel nea en dd ed airport is significantly lower than at the destination airport. the return flight and performing only partial refueling at destination. There are two types of fuel tankering: ● Full (fuel) tankering, which consists in transporting all the fuel needed for the return ● for the r Pa flight f rtial r(om f eu turn e the departure l) t flight ankeriand pe ng, whi ai rformin rport to a ch consi g on sv ts in oid refuel ly part tranis ap l re io nr g a tfu ineling tg the desti onl at y p dest ar nta o itn ion ai f t at h ion. e frport, u e l nea en dd ed There are two types of fuel tankering: Under the European Union Aviation Safety Agency regulations (CAT.OP.MPA.150 Fuel ●● Pa f Ful light f rtia l (fue l r(om fl) u t e the departure a l) n t k aering nkeri,n wh g, whi ich ai cons rport to a ch consi ists in sv ts in t oid refuel rantsporti ransping al o nr g a tint l the fuel g the desti only pa needed f r nta o tion ai f theo frport, r the return uel nea en dd ed for the return flight and performing only partial refueling at destination. Under the European Union Aviation Safety Agency regulations (CAT.OP.MPA.150 policy), before departure, the captain must ensure that every flight carries sufficient fuel ● Full (fuel) tankering, which consists in transporting all the fuel needed for the return ● for the r Pa flight f rtial r(om f eu turn e the departure l) t flight ankeriand pe ng, whi ai rformin rport to a ch consi g on sv ts in oid refuel ly part tranis ap l re io nr g a tfu ineling tg the desti onl at y p dest ar nta o itn ion ai f t at h ion. e frport, u e l nea en dd ed Under the European Union Aviation Safety Agency regulations (CAT.OP.MPA.150 Fuel policy), before departure, the captain must ensure that every flight carries sufficient for the planned operation and reserves to cover deviations from the planned operation: ● Pa flight f rtial r(om fue the departure l) tankering, whi airport to a ch consisv ts in oid refuel transpio nr g a tintg the desti only par nta o tion ai f the frport, uel nea en dd ed for the return flight and performing only partial refueling at destination. Fuel po Under t licy), h before dep e European Un arture, the c ion Avaiat ptain must ion Safety ens Agenc ure ty h r at e every f gulation light s (C carr AT.OP. ies s MPA uffic.ient 150 fuel for the planned operation and reserves to cover deviations from the planned opera- ● for the r Partial (f eu turn el) t flight ankeriand pe ng, whi rformin ch consi g on sts in ly part tranis ap l re ortfu ineling g onl at y p dest art o in f t at h ion. e fu e l needed Taxi fuel: The fuel necessary for taxi, which should not be less than the amount ti fue Fuel po on: l fUnder t or t lic hy), e ph before dep lanned op e European Un e arrture, the c ation ioand re n Avaiat ptain must ser ion ves t Safet o cov y ens Agenc er ur dev e ty h i r at at eions every f gulafr tion om light s (C th carr e p AT.OP. lann ies e s MPA d op uffic.er ient 150 a- for the return flight and performing only partial refueling at destination. expected to be used prior to take-off; Fuel po Under t licy), h before dep e European Un arture, the c ion Avaiat ptain must ion Safety ens Agenc ure ty h r at e every f gulation light s (C carr AT.OP. ies s MPA uffic.ient 150 ti fue on: l for the planned operation and reserves to cover deviations from the planned opera- ● Taxi fuel: The fuel necessary for taxi, which should not be less than the amount Trip fuel: The fuel required from the start of take-off, through climb, cruise, descent, ti fue Fuel po on: l fUnder t or t lic hy), e ph before dep lanned op e European Un e arrture, the c ation ioand re n Avaiat ptain must ser ion ves t Safet o cov y ens Agenc er ur dev e ty h i r at at eions every f gulafr tion om light s (C th carr e p AT.OP. lann ies e s MPA d op uffic.er ient 150 a- ● expected to be used pr Taxi fuel: The fuel nec ior t essary o take for t -off; axi, which should not be less than the amount and approach to touchdown at destination; Fuel policy), before departure, the captain must ensure that every flight carries sufficient ti fue on: l for the planned operation and reserves to cover deviations from the planned opera- ● Taxi fuel: The fuel necessary for taxi, which should not be less than the amount ● Trip f expected to be used pr uel: The fuel requior t iredo from t take-off; he start of take-off, through climb, cruise, descent, Reserve fuel consisting of: fuel for the planned operation and reserves to cover deviations from the planned opera- tion: ●● Trip f expected to be used pr Taxi fuel: Th uel: Thee fuel nec fuel requior t ire essary do from t take for t -off; ha e st xi, awhich sho rt of take-of ufld not be less than the am , through climb, cruise, desc ount ent, and approach to touchdown at destination; tion: # Contingency fuel (3 to 5%): This fuel is carried to cover unforeseen variations ● Taxi fuel: The fuel necessary for taxi, which should not be less than the amount ●● Rese and Trip f expected to be used pr ap rve f up elr : The oach uel c fue t onsist o t lo re uchdow iqu ngior t ire ofd : o from t n at take de -off; h st e st inat ar it o of t n; ake-off, through climb, cruise, descent, from the planned operation. For example, different winds or temperatures ●● Trip f expected to be used pr Taxi fuel: Th uel: Thee fuel nec fuel requior t ire essary do from t take for t -off; ha e st xi, awhich sho rt of take-of ufld not be less than the am , through climb, cruise, desc ount ent, ● Rese and ap rve f proach uel c t onsist o touchdow ing of: n at destination; ○ Contingency fuel (3 to 5%): This fuel is carried to cover unforeseen variations from forecast, or air traffic control restrictions on levels and speed. It can be ● and Trip f expected to be used pr ap up elr : The oach fue to t lo re uchdow quior t iredo from t n at take de -off; h st e st inat ar it o of t n; ake-off, through climb, cruise, descent, ● Reserve fuel consisting of: ○ from the plan Contingency ned operatio fuel (3 to 5%n. For ex ): This fu ample, el is carr diffe ied rent to co wiver un nds or t fore emperat seen var ureisat from ions used any time after dispatch (once aircraft moves under its own power). It ●● Rese and Trip f ap rve f up elr : The oach uel c fue t onsist o t lo re uchdow iqu ngire ofd : from t n at deh st e st inat ar it o of t n; ake-off, through climb, cruise, descent, ○ Contingency fuel (3 to 5%): This fuel is carried to cover unforeseen variations forec from the plan ast, or air traffic contr ned operation. For ex ol restrict ample, ions on levels different and winds or t speed. It can emperat be used ures from any cannot be planned to use before. More likely, it is used for delays on departure and approach to touchdown at destination; ● Reserve fuel consisting of: ○ forec from the plan Contingency ast, or air traffic contr ned operatio fuel (3 to 5%n. For ex o ):l restrict This fu ample, el ions is on levels carr diffe ied rent toand co wiver un nds or t speed. It can fore emperat seen be used var ureisat from ions any time after dispatch (once aircraft moves under its own power). It cannot be or arrival; ● Reserve fuel consisting of: ○ Contingency fuel (3 to 5%): This fuel is carried to cover unforeseen variations time after forec from the plan ast, or air traffic contr dispatch ned operatio (once n. For ex oairc l restrict raft move ample, ions on levels s un diffe der rent its o and winds or t speed. It can wn power). I emperat be used t cannot be ures from any planned to use before. More likely, it is used for delays on departure or arrival; # Alternate fuel: The fuel to cover a possible “Go around” or a landing at an ○ from the plan Contingency ned operatio fuel (3 to 5%n. For ex ): This fu ample, el is carr diffe ied rent to co wiver un nds or t fore emperat seen var ureisat from ions ○ planned time after forec Altern ast, or air traffic contr at to u e fu dispatch el se before : The fu(once el t . Mo o c r oairc e o l restrict l vie kel raft move r a p y, o it i ions sss ib u on levels ls un e sed “Gfor de der o ar its o ound and lay speed. It can sw ” or on dep n power). I a land artur ing e or be used t at cannot be an arr alt ival; any er- alternate airport; time after forec from the plan ast, or air traffic contr dispatch ned operatio (once n. For ex oairc l restrict raft move ample, ions on levels s un diffe der rent its o and winds or t speed. It can wn power). I emperat be used t cannot be ures from any ○ planned na Alt te ai ernat rport; to u e fuel se before : The fuel t . Mo o c re o l vie kel r a p y, o it i sss ib u le sed “Gfor de o around lays” or on dep a land artur ing e or at an arr alt ival; er- # Final reserve: For 30 min at International Standard Atmosphere 1500 feet above ○ planned time after forec Altern ast, or air traffic contr at to u e fu dispatch el se before : The fu(once el t . Mo o c r oairc e o l restrict l vie kel raft move r a p y, o it i ions sss ib u on levels ls un e sed “Gfor de der o ar its o ound and lay speed. It can sw ” or on dep n power). I a land artur ing e or be used t at cannot be an arr alt ival; any er- ○ na Fina te ai l rese rport; rve: For 30 min at International Standard Atmosphere 1500 feet above the alternate airport; time after dispatch (once aircraft moves under its own power). It cannot be ○ planned na Alt te ai ernat rport; to u e fuel se before : The fuel t . Mo o c re o l vie kel r a p y, o it i sss ib u le sed “Gfor de o around lays” or on dep a land artur ing e or at an arr alt ival; er- ○ t Fina he alt l rese ernat rve e:airp Forort 30; m in at International Standard Atmosphere 1500 feet above # Discretionary fuel (or 15 min of holding fuel if the flight is planned with planned to use before. More likely, it is used for delays on departure or arrival; ○○ na Alt t Fina he alt te ai ern l rese e at rport; rn e fu at rve e: el airp For : The fu ort 30; m el t in oat co Int vee r a p rnat o ion ssib all St e “G ano a dar rd ound Atm ” or ospa l here and 15 ing 00 at feet an ab alt ov ere - ○ Discretionary fuel (or 15 min of holding fuel if the flight is planned with no al- no alternate (go-around at destination, climb, cruise, descent, approach, and ○ na Alt te ai ernat rport; e fuel: The fuel to cover a possible “Go around” or a landing at an alter- ○○ t Fina Discret th ernat e alt l rese e ( eirn on gat o- rv ar e ar e: yairp For ound fueort 3 l (o 0 at ; m r 1 dest i5 n m at in i Int n of ho ation, ernat cl ldin ion imb g a,l cru St fuel an i if se, dar the fl desc d At e ight i n m t,o ap sp s here p planned roach, 150and 0with no al- feet lan ab dov ing e landing at the selected alternate airport); ○ na t Fina he alt te ai l rese e rport; rnat rve e:airp Forort 30; m in at International Standard Atmosphere 1500 feet above ○ Discret a te trnat the sel e ( ion g eo- cted al ar ar yound fue terna l (o atr 1 dest te 5airport) m in in of ho ation, ; cl ldin imb g , cru fuel i if se, the fl desce ight i nt, ap s p planned roach, and with no al- landing # Extra fuel, which should be at the discretion of the commander. ○○ t Fina Discret th ernat e alt l rese e ( eirn on gat o- rv ar e ar e: yairp For ound fueort 3 l (o 0 at ; m r 1 dest i5 n m at in i Int n of ho ation, ernat cl ldin ion imb g a,l cru St fuel an i if se, dar the fl desc d At e ight i n m t,o ap sp s here p planned roach, 150and 0with no al- feet lan ab dov ing e ○ a Extra t the sel fuel e, whi cted al ch shoul ternate dairport) be at the di ; scretion of the commander. In other words, fuel tankering is the practice of adding more fuel than what is required ○ t Discret a th e trnat the sel e alte ( eirn on g eat o- cted al ar e ar yairp ound fue terna ort l (o at ; r 1 dest te 5airport) m in in of ho ation, ; cl ldin imb g , cru fuel i if se, the fl desce ight i nt, ap s p planned roach, and with no al- landing ○ Extra fuel, which should be at the discretion of the commander. In other words, fuel tankering is the practice of adding more fuel than what is re- by the fuel policy for a safe flight. ○ Discretionary fuel (or 15 min of holding fuel if the flight is planned with no al- ○ a t Extra e trnat the sel fuel e (g eo- , whi cted al around ch shoul terna at dest te dairport) bie n a at tion, the di ; clim screti b, cru on of ise, the desc comma ent, ap nder. proach, and landing In other words, fuel tankering is the practice of adding more fuel than what is re- quired by the fuel policy for a safe flight. a te trnat the sel e (g eo- cted al around terna at dest te airport) ination, ; climb, cruise, descent, approach, and landing ○ Extra fuel, which should be at the discretion of the commander. 3. Purpose of This Study quired In by t othe hre w fuo el po rds, lic fuy fo el ta r a nk s ea rfe in f glight is th . e practice of adding more fuel than what is re- ○ a Extra t the sel fuel e, whi cted al ch shoul ternate dairport) be at the di ; scretion of the commander. In other words, fuel tankering is the practice of adding more fuel than what is re- 3. quPurpos ired by t e of he This S fuel potlic ud y fo y r a safe flight. Until now, the very few studies on fuel tankering [3–9] have focused mainly on its ○ Extra fuel, which should be at the discretion of the commander. 3. quPurpos ired In by t ote of he hre w This S fuo el po rds,t lic ud fuy fo eyl t a r a nk s ea rfe in f glight is th . e practice of adding more fuel than what is re- economic benefits for a single or a limited number of flight. 3. quPurpos ired In by t ote of he hre w This S fuo el po rds,t lic ud fuy fo eyl t a r a nk s ea rfe in f glight is th . e practice of adding more fuel than what is re- However, as illustrated on Figure 1, when a return flight between two airports A and 3. quPurpos ired by t e of he This S fuel potlic ud y fo y r a safe flight. B, carry part or all of the fuel needed for its return flight (B-A), an “extra” amount of fuel is 3. Purpose of This Study burnt just to carry that additional fuel on the first leg (A-B). This is because the additional 3. Purpose of This Study fuel carried when doing fuel tankering increases the weight of the aircraft and thus its fuel consumption, resulting in additional CO emissions. ICAO Doc 10013 [2] indicates Aerospace 2021, 8, x FOR PEER REVIEW 3 of 16 Until now, the very few studies on fuel tankering [3–9] have focused mainly on its economic benefits for a single or a limited number of flight. However, as illustrated on Figure 1, when a return flight between two airports A and B, carry part or all of the fuel needed for its return flight (B-A), an “extra” amount of fuel is burnt just to carry that additional fuel on the first leg (A-B). This is because the addi- tional fuel carried when doing fuel tankering increases the weight of the aircraft and thus its fuel consumption, resulting in additional CO2 emissions. ICAO Doc 10013 [2] indicates that “The extra fuel burn attributable to additional weight carried on board an aircraft is typically on the order of 2.5 to 4.5% of the additional weight, per hour of flight, depending on the characteristics of the aircraft.” Fuel tankering has therefore an environmental im- pact. As the demand to accelerate the decarbonization of transport becomes more and more pressing, it is relevant to estimate the extent of the environmental impact of fuel tankering. The purpose of this paper is to present the results of a first study whose aim Aerospace 2021, 8, 37 3 of 16 was to estimate what the impact of fuel tankering would be at ECAC level in 2018 on the basis of the actual collected data (i.e.,: fuel prices at airports in June 2018, and passenger load that f “The actor ext at ra that fuel time, burn etattributable c.). In the futto uradditional e, it would be weight intere carried sting ton o car boar ry o du an t sair ens craft itivitis y ana typically lyses t on o se the e tor he econom der of 2.5ic tolimit 4.5%s of of t the his pr additional actice by weight, varying per fuel hour prices and of flight, un depending der dif- on the characteristics of the aircraft.” Fuel tankering has therefore an environmental impact. ferent hypotheses of passenger load factor, etc. Figure 1. Example of extra fuel burn for a return flight between two airports with and without fuel Figure 1. Example of extra fuel burn for a return flight between two airports with and without tankering. fuel tankering. As the demand to accelerate the decarbonization of transport becomes more and more pressing, it is relevant to estimate the extent of the environmental impact of fuel tankering. The purpose of this paper is to present the results of a first study whose aim was to estimate what the impact of fuel tankering would be at ECAC level in 2018 on the basis of the actual collected data (i.e.,: fuel prices at airports in June 2018, and passenger load factor at that time, etc.). In the future, it would be interesting to carry out sensitivity analyses to see the economic limits of this practice by varying fuel prices and under different hypotheses of passenger load factor, etc. 4. Study The study was conducted with the following steps, data, and assumptions. 4.1. Steps of the Study STEP 1: Verify that fuel tankering is a common practice that deserves to be studied and that no regulatory instruments already exist to dissuade airlines from tankering fuel or to compensate for its impact on the environment; Aerospace 2021, 8, 37 4 of 16 STEP 2: Calculate the fuel tankering efficiency with EUROCONTROL Base of Aircraft Data (BADA) models based on typical types of aircraft flying in ECAC airspace and for all the possible distances flown; STEP 3: Calculate the number of flights for which full or partial tankering is opera- tionally possible; STEP 4: Estimate the economic opportunity of tankering. 4.2. Data Used and Assumptions The statistics required for the calculations were derived from June 2018 traffic in the ECAC area; The estimated tankering results for this month has been extrapolated to a year by applying a linear extrapolation based on the number of flights for which fuel tankering was feasible. However, the extrapolation made does not take account of any influence of seasonal traffic patterns; The study covered aircraft models representing 66% of flights in ECAC; Aircraft performance was based on EUROCONTROL BADA model. BADA is the international reference in aircraft performance modeling for trajectory prediction and simulation. Based on the best available reference data on aircraft performance, BADA reproduces realistically the geometric, kinematic and kinetic aspects of aircraft’s behaviour over the entire operational flight envelope and in all phases of flight; The optimal flight level calculated for performing full fuel tankering was used in the model. The following limits have been taken into account: Maximum take-off weight, Maxi- mum landing weight, Maximum fuel load of each aircraft type; An average 20 min was used for the taxi-out; This value was calculated using average taxi-out times provided by EUROCONTROL Central Office of Delay Analysis for the busiest European airports; The CO emission factor used is 3.15 kg CO per kg of fuel burn; 2 2 Fuel prices negotiated at 140 airports in ECAC from 2 major airlines were used; The payload was calculated with a load factor of 80.3% [10] and 124 kg/passenger; A profit threshold of  30 was used as a pivotal point in the decision to go into fuel tankering; but this is a very cautious assumption as some airlines use  15 as a pivotal point; A cost of  20/tonne has been set for a tonne of CO allowances; this is also a very conservative assumption because not every tonne of CO requires the purchase of CO allowances; In the tables presented in our study “Trip fuel” is composed of the following elements: Taxi + Climb Cruise Descent + Approach to Touchdown. The “Reserve fuel” is composed of the following elements: Contingency + Alternate + Final reserve; When, for a round trip, both full and partial fuel tankering were possible, our model always privileged full fuel tankering. 4.3. Flights Excluded from the Study Military flights performed by military aircraft and customs and police flights; search and rescue; state flights; Flights not performed under instrument flight rules (IFR) only. 4.4. Study Limitations Due to the coverage of airline negotiated fuel price data we were able to access, the study was limited to flights up to 1500 (Full tankering) and 2500 NM (Partial tankering). As a result, the aircraft models considered are mainly operated on short and medium-haul. Furthermore, due to the physical fuel capability of the aircraft models considered: # For full tankering, flight legs of more than 1500 NM were not considered, Aerospace 2021, 8, 37 5 of 16 # For partial tankering, flight legs of more than 2500 NM were not considered. The impact of fuel tankering for reasons other than fuel price differences at airports was not considered (e.g., shorten turnaround or fuel shortage). The possibility of tankering fuel for more than one leg, which the software of some airlines is able to calculate, has not been estimated. 4.5. STEP 1: Verify That Fuel Tankering Is a Common Practice That Deserves to Be Studied and That No Regulatory Instruments Already Exist to Dissuade Airlines from Tankering Fuel or to Compensate for Its Impact on the Environment We started by conducting a series of interviews of pilots from airlines, business aviation dispatchers and handling agents. They confirmed that fuel tankering was a practice commonly used by airlines. They reported that 15% of the time they are performing full fuel tankering, and another 15% for partial fuel tankering. They also reported that fuel tankering is done in 90% of cases for fuel price reasons, and only in 10% of cases for social disruption, technical failures at the refueling facility, fuel shortages, risks of delays, or contaminated fuel at destination airports. In fact, this practice is so common that, to assist the captain in calculating the optimum tankering, most airlines use operations centre software (e.g., Lido and Sabre) that ensures compliance with fuel policy but also takes into account the cost of fuel that the airline has negotiated at the airports it serves to determine the maximum amount of fuel that could be added on top if cost-effective. A patent has recently been published by Honeywell for a tool to further enhance fuel tankering and fully exploit its economic benefits [11]. Unexpectedly, in ICAO Doc. 10013 [2], which deals with “Operational Opportunities to Reduce Fuel Burn and Emissions”, the recommendation to reduce the use of fuel tankering is presented as a measure to reduce cost rather than highlighting the amount of additional emissions it generates, particularly CO emissions. Then, we investigated whether instruments already exist to limit its practice or com- pensate for its environmental impact. The only instrument currently in place that could have had this effect is the European Union Emissions Trading Scheme (EU ETS). However, the inclusion of aviation in the CO European EU ETS currently in place is not sufficient to limit the practice of tankering for economic reasons. First of all, Aviation EU ETS only covers flights within the European Union and therefore excludes flights for which one of the two airports served is located outside this area. For example, flights from Africa, America, Asia, China, Middle East, or Russia, are not subject to the EU ETS. In addition, as of today, 85% of the CO emission quotas of the aviation EU ETS, determined when the baseline was established, are still free of charge. Furthermore, as pointed out by Daley and Preston, in [12], care should be taken to ensure that the introduction of new policies does not amplify the practice of tankering. [12] quotes: “if fuel taxes were not introduced globally, economic distortions could occur, creating an incentive for airlines to uplift cheaper fuel—by tinkering—in countries where the tax did not apply, with the net effect that aviation emissions could increase—hereby negating the original purpose of the tax (Wit et al., 2004, p. 43)”. However, as we observed in STEP 2, even in this case, this phenomenon would be limited by the physical capability of the aircraft to perform tankering and the possibility for airlines to adapt their business model to this new tax and the new possible traffic patterns. The purpose of this study is not to address the influence that new policies could have on the practice of tankering. 4.6. STEP 2: Identify When Fuel Tankering Is Operationally Feasible in ECAC The capacity of aircraft to transport fuel is not infinite. Multiple factors influence the amount of fuel an aircraft can carry for a specific flight. It depends on the aircraft model, the type of engines it is equipped with, the size and options of the fuel tank fitted, its maximum take-off and landing weight, the distance flown, the specific conditions and situation at each airport and, most importantly, its payload. Aerospace 2021, 8, x FOR PEER REVIEW 6 of 16 4.6. STEP 2: Identify When Fuel Tankering Is Operationally Feasible in ECAC The capacity of aircraft to transport fuel is not infinite. Multiple factors influence the amount of fuel an aircraft can carry for a specific flight. It depends on the aircraft model, Aerospace 2021, 8, 37 6 of 16 the type of engines it is equipped with, the size and options of the fuel tank fitted, its maximum take-off and landing weight, the distance flown, the specific conditions and situation at each airport and, most importantly, its payload. The first step is therefore to estimate, for each type of aircraft, its capacity to carry The first step is therefore to estimate, for each type of aircraft, its capacity to carry different amounts of additional fuel (the amount of tankering in % of the fuel necessary different amounts of additional fuel (the amount of tankering in % of the fuel necessary for the return flight) over different distances, for different flight levels, and the amount of for the return flight) over different distances, for different flight levels, and the amount of extra fuel burn due to the transport of this additional fuel. This was established with the extra fuel burn due to the transport of this additional fuel. This was established with the help of BADA. help of BADA. Figure 2 is an example of the “extra” fuel burn for one of the most representative Figure 2 is an example of the “extra” fuel burn for one of the most representative aircraft models flying in ECAC for several distances and flight levels over which it can be aircraft models flying in ECAC for several distances and flight levels over which it can be operated. It can be seen that the % of extra fuel burnt on the first leg A to B, while carrying operated. It can be seen that the % of extra fuel burnt on the first leg A to B, while carrying the full fuel required for the return leg B to A, varies a lot depending on the flight level, the full fuel required for the return leg B to A, varies a lot depending on the flight level, distance flown, and the % of tankering carried (due to the additional weight). distance flown, and the % of tankering carried (due to the additional weight). Figure 2. % of extra fuel burnt for full fuel tankering on various flight distances for a specific aircraft model. Figure 2. % of extra fuel burnt for full fuel tankering on various flight distances for a specific aircraft model. Figure 2 also helps to determine the % of extra fuel burnt at a flight level by a specific Figure 2 also helps to determine the % of extra fuel burnt at a flight level by a specific aircraft model. aircraft model. Each aircraft weight has its own optimum flight level for a given distance. This is what is consider here, we determine the optimal flight level taking into account the new aircraft weight when performing full fuel tankering. However, when reading it, it should not be concluded that the lower % of “extra” fuel burnt at the lowest flight levels (e.g., FL 290) translates into lower overall fuel consumption compared to higher flight levels (e.g., FL 350). Indeed, at these flight levels, the aircraft is well below its optimum cruising level, and will therefore consume much more fuel than at flight levels closer to this optimum. It is therefore necessary to convert to absolute kg of Aerospace 2021, 8, x FOR PEER REVIEW 7 of 16 Each aircraft weight has its own optimum flight level for a given distance. This is what is consider here, we determine the optimal flight level taking into account the new aircraft weight when performing full fuel tankering. However, when reading it, it should not be concluded that the lower % of “extra” fuel burnt at the lowest flight levels (e.g., FL 290) translates into lower overall fuel con- sumption compared to higher flight levels (e.g., FL 350). Indeed, at these flight levels, the aircraft is well below its optimum cruising level, and will therefore consume much more Aerospace 2021, 8, 37 7 of 16 fuel than at flight levels closer to this optimum. It is therefore necessary to convert to ab- solute kg of total fuel burnt to determine the optimum flight level to be used for carrying total fuel burnt to determine the optimum flight level to be used for carrying the “extra” the “extra” fuel tankered. fuel tankered. Figure 3 shows that for a 600 NM flight of this aircraft model, the absolute minimum Figure 3 shows that for a 600 NM flight of this aircraft model, the absolute minimum fuel burnt for carrying all the fuel required for the return flight (“full fuel tankering”) will fuel burnt for carrying all the fuel required for the return flight (“full fuel tankering”) will be obtained if the flight is cruising at 36,000 ft (FL 360). The percentage of extra fuel burn be obtained if the flight is cruising at 36,000 ft (FL 360). The percentage of extra fuel burn compared to the fuel burn for one trip at its optimum flight level (36,000 ft or FL 360) compared to the fuel burn for one trip at its optimum flight level (36,000 ft or FL 360) compared to other possible flight levels is highlighted in Figure 4. This percentage of ad- compared to other possible flight levels is highlighted in Figure 4. This percentage of ditional fuel burn is useful in determining the threshold at which it will be cost effective additional fuel burn is useful in determining the threshold at which it will be cost effective to tanker fuel, as exp to tanker lai fuel, ned bel as explained ow. below. Figure 3. Total fuel burnt (kg) for full fuel tankering at various flight levels (hundreds of feet). Figure 3. Total fuel burnt (kg) for full fuel tankering at various flight levels (hundreds of feet). In this study, it was assumed that all flights would fly at their optimum flight level, but In this study, it was assumed that all flights would fly at their optimum flight level, in reality, this is not always possible due to limited en route capacity or flight level capping but in reality, this is not always possible due to limited en route capacity or flight level between two city pairs (e.g., Between Paris and Frankfurt, flights are capped at 23,000 ft capping between two city pairs (e.g., Between Paris and Frankfurt, flights are capped at (FL 230) in one direction and 24,000 ft (FL 240) in the other direction, and are therefore 23,000 ft (FL 230) in one direction and 24,000 ft (FL 240) in the other direction, and are burning even more fuel to carry the extra fuel compared to flying closer to 36,000 ft (FL 360) therefore burning even more fuel to carry the extra fuel compared to flying closer to 36,000 for this distance and weight. Consequently, in this study the extra fuel burn estimates due to tankering are very conservative. ft (FL 360) for this distance and weight. Consequently, in this study the extra fuel burn Let us take the example of one of the most representative short-medium haul European estimates due to tankering are very conservative. aircraft on a 600 NM round trip flight, a distance close to the average distance of 585 NM for ECAC flight, between two airports A and B (Figure 5). The total weight of the aircraft model chosen consists of 43.7 tonnes of empty operating weight, plus 17.6 tonnes of payload, and 4.5 tonnes of fuel consisting of 3.6 tonnes for the flight and 0.9 tonnes of reserve and taxi. This model has a maximum fuel load capacity of 23.5 tonnes of fuel, and a maximum take-off weight of 77 tonnes. Aerospace 2021, 8, x FOR PEER REVIEW 8 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 8 of 16 Aerospace 2021, 8, 37 8 of 16 Figure 4. % of extra fuel burnt for various flight distances for a specific aircraft mode with optimum flight cruise level determined. Let us take the example of one of the most representative short-medium haul Euro- pean aircraft on a 600 NM round trip flight, a distance close to the average distance of 585 NM for ECAC flight, between two airports A and B (Figure 5). The total weight of the aircraft model chosen consists of 43.7 tonnes of empty operating weight, plus 17.6 tonnes of payload, and 4.5 tonnes of fuel consisting of 3.6 tonnes for the flight and 0.9 tonnes of Figure 4. % of extra fuel burnt for various flight distances for a specific aircraft mode with optimum Figure 4. % of extra fuel burnt for various flight distances for a specific aircraft mode with optimum flight cruise level deter- reserve and taxi. This model has a maximum fuel load capacity of 23.5 tonnes of fuel, and flight cruise level determined. mined. a maximum take-off weight of 77 tonnes. Let us take the example of one of the most representative short-medium haul Euro- pean aircraft on a 600 NM round trip flight, a distance close to the average distance of 585 NM for ECAC flight, between two airports A and B (Figure 5). The total weight of the aircraft model chosen consists of 43.7 tonnes of empty operating weight, plus 17.6 tonnes of payload, and 4.5 tonnes of fuel consisting of 3.6 tonnes for the flight and 0.9 tonnes of reserve and taxi. This model has a maximum fuel load capacity of 23.5 tonnes of fuel, and a maximum take-off weight of 77 tonnes. Figure 5. Example for a 600 NM flight with no tankering. Figure 5. Example for a 600 NM flight with no tankering. When not doing tankering (Figure 5), the fuel consumption of this aircraft model over When not doing tankering (Figure 5), the fuel consumption of this aircraft model over tthis his d distance istance iis s 3 3.59 .59 ttonnes. onnes. O On n a arrival rrival a at t a airport irport B B, , tther here e iis s 0 0.7 .7 ttonnes onnes o of f r re eserve serve ffuel uel lleft, eft, and the total and the total weight of the weight of the airc aircraft raft does does not exceed 66 tonnes certified maxim not exceed 66 tonnes certified maximum um land landing ing weight weight fo for r a s a safe afe llanding. anding. By tanker By tankering ing all all the fuel n the fuel needed eeded fo for the r the return le return leg (B-A) g (B-A) from from airport airpA ort A over a over a 600 NM 600 flight (Figure 6), this flight burns 167 kg of fuel on top of the 3.59 tonnes of fuel burnt when NM flight (Figure 6), this flight burns 167 kg of fuel on top of the 3.59 tonnes of fuel burnt Figure 5. Example for a 600 NM flight with no tankering. not doing tankering. This represents 4.66% more fuel burnt. Consequently, if the fuel price when not doing tankering. This represents 4.66% more fuel burnt. Consequently, if the negotiated by its airline operator at the destination airport B is 4.66% more expensive than When not doing tankering (Figure 5), the fuel consumption of this aircraft model over at the departure airport A, and that the potential cost saving is above the profit threshold, it this distance is 3.59 tonnes. On arrival at airport B, there is 0.7 tonnes of reserve fuel left, might be worthwhile for this operator, from an economic point of view, to decide to tanker and the total weight of the aircraft does not exceed 66 tonnes certified maximum landing all the fuel necessary for the return flight (B-A) from the departure airport A. weight for a safe landing. By tankering all the fuel needed for the return leg (B-A) from airport A over a 600 NM flight (Figure 6), this flight burns 167 kg of fuel on top of the 3.59 tonnes of fuel burnt when not doing tankering. This represents 4.66% more fuel burnt. Consequently, if the Aerospace 2021, 8, x FOR PEER REVIEW 9 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 9 of 16 fuel price negotiated by its airline operator at the destination airport B is 4.66% more ex- fuel price negotiated by its airline operator at the destination airport B is 4.66% more ex- pensive than at the departure airport A, and that the potential cost saving is above the pensive than at the departure airport A, and that the potential cost saving is above the profit threshold, it might be worthwhile for this operator, from an economic point of view, profit threshold, it might be worthwhile for this operator, from an economic point of view, Aerospace 2021, 8, 37 to decide to tanker all the fuel necessary for the return flight (B-A) from the depart 9 of ure 16 to decide to tanker all the fuel necessary for the return flight (B-A) from the departure airport A. airport A. Figure 6. Example for a 600 NM flight performing a full (100%) tankering. Figure 6. Figure 6. Example for a Example for a 600 600 NM flight perf NM flight performing orming a full (10 a full (100%) 0%) tankering. tankering. However, above 600 NM, it is no longer possible for this aircraft model to do full However, above 600 NM, it is no longer possible for this aircraft model to do full However, above 600 NM, it is no longer possible for this aircraft model to do full tankering, only partial tankering could be envisaged. tankering, only partial tankering could be envisaged. tankering, only partial tankering could be envisaged. Let us take the example of a 900 NM flight with the same aircraft model as before, Let us take the example of a 900 NM flight with the same aircraft model as before, Let us take the example of a 900 NM flight with the same aircraft model as before, same empty operating weight of 43.7 tonnes, same payload of 17.6 tonnes, same maximum same empty operating weight of 43.7 tonnes, same payload of 17.6 tonnes, same maximum same empty operating weight of 43.7 tonnes, same payload of 17.6 tonnes, same maximum fuel load capacity of 23.5 tonnes of fuel, and same maximum take-off weight of 77 tonnes. fuel load capacity of 23.5 tonnes of fuel, and same maximum take-off weight of 77 tonnes. fuel load capacity of 23.5 tonnes of fuel, and same maximum take-off weight of 77 tonnes. It wi It will ll need 6.4 tonnes of need 6.4 tonnes of fuel fuel to perf to perform orm thi this flight, s flight, consi consisting sting of 5 of 5.2 tonnes .2 tonnes f for the or trip the and trip It will need 6.4 tonnes of fuel to perform this flight, consisting of 5.2 tonnes for the trip and 1.2 tonnes o 1.2 tonnes of reserve. f reserv When e. When not not doing do tankering ing tankering ( (Figur Figure 7 e 7), the ), t fuel he fconsumption uel consumptof ion of this and 1.2 tonnes of reserve. When not doing tankering (Figure 7), the fuel consumption of tair his a craft ircr model aft model over t over this distance his distanc is now e is now 5 5.19 tonnes. .19 tonnes. On On arrival arat riva airport l at aiB, rport ther B, there is e is 1 tonne 1 this aircraft model over this distance is now 5.19 tonnes. On arrival at airport B, there is 1 tonne of re of reserve fuel serve fuel le left, and ft, theand the total total weight weig of the ht of the aircraft aircr doesa not ft doe exceed s not exceed 66 tonnes 66 tonnes certified tonne of reserve fuel left, and the total weight of the aircraft does not exceed 66 tonnes cert maximum ified ma landing ximum weight landing for weight a safe for a sa landing. fe landing. certified maximum landing weight for a safe landing. Figure 7. Example for a 900 NM flight with no tankering. Figure 7. Example for a 900 NM flight with no tankering. Figure 7. Example for a 900 NM flight with no tankering. Under the same operational assumptions mentioned above, this type of aircraft can- Under the same operational assumptions mentioned above, this type of aircraft can- Under the same operational assumptions mentioned above, this type of aircraft cannot not do 100% fuel tankering on a 900 NM flight but only a maximum of 50%, otherwise it not do do 100% 100% fuel ftankering uel tankerin ong a on 900aNM 900 flight NM fbut light only buta on maximum ly a maxim of u 50%, m ofotherwise 50%, othe it rwise would it would exceed its authorized landing weight at airport B. At 50% fuel tankering (Figure 8), would exceed excee its authorized d its authori landing zed land weight ing wat eight airport at airp B. o At rt 50% B. Atfuel 50%tankering fuel tanke (Figur ring (Figure 8) e 8), this , this flight burns 3.66% more fuel than if it had not carried that “extra” fuel. Consequently, flight burns 3.66% more fuel than if it had not carried that “extra” fuel. Consequently, if this flight burns 3.66% more fuel than if it had not carried that “extra” fuel. Consequently, if the fuel price negotiated by its airline operator at the destination airport B is 3.66% more the fuel price negotiated by its airline operator at the destination airport B is 3.66% more if the fuel price negotiated by its airline operator at the destination airport B is 3.66% more expensive than at the departure airport A, it might be worthwhile for this operator, from expensi expensive ve than a than att the the departur departure e ai arport irport A, A, itit might might be worthwhi be worthwhile lfor e for thi this operator s operat,or, from from an Aerospace 2021, 8, x FOR PEER REVIEW 10 of 16 an economic point of view, to decide to tanker 50% of the fuel necessary for the return economic point of view, to decide to tanker 50% of the fuel necessary for the return flight an economic point of view, to decide to tanker 50% of the fuel necessary for the return flight (B-A) from the departure airport A. (B-A) from the departure airport A. flight (B-A) from the departure airport A. Figure 8. Example for a 900 NM flight performing a 50% partial fuel tankering. Figure 8. Example for a 900 NM flight performing a 50% partial fuel tankering. 4.7. STEP 3: Calculate the Number of Flights for Which Full or Partial Tankering Is Operationally Possible After having determined the tankering capability for each aircraft model, it is neces- sary to estimate how many aircraft of the same model operated in ECAC could potentially do tankering and at what percentage level. This is illustrated in Figure 9, which shows for one specific aircraft model the percentage of fuel tankering possible as a function of the flight distance in NM and the percentage of additional fuel burnt. Figure 9. % of extra fuel burn as a function of % of tankering and distance flown for a specific aircraft model. Once the percentage of tankering capacity for this aircraft model for several theoret- ical distance flown are obtained, they have been applied to the real traffic in ECAC grouped by distance flown as illustrated in Figure 10. Figure 10. % of flight and % of feasible tankering per distance. Aerospace 2021, 8, x FOR PEER REVIEW 10 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 10 of 16 Aerospace 2021, 8, 37 10 of 16 Figure 8. Example for a 900 NM flight performing a 50% partial fuel tankering. Figure 8. Example for a 900 NM flight performing a 50% partial fuel tankering. 4.7. STEP 3: Calculate the Number of Flights for Which Full or Partial Tankering Is 4.7. STEP 3: Calculate the Number of Flights for Which Full or Partial Tankering Is 4.7. STEP 3: Calculate the Number of Flights for Which Full or Partial Tankering Is Operationally Possible Operationally Possible Operationally Possible After having determined the tankering capability for each aircraft model, it is necessary After having determined the tankering capability for each aircraft model, it is neces- After having determined the tankering capability for each aircraft model, it is neces- to estimate how many aircraft of the same model operated in ECAC could potentially do sary to estimate how many aircraft of the same model operated in ECAC could potentially sary to estimate how many aircraft of the same model operated in ECAC could potentially tankering and at what percentage level. This is illustrated in Figure 9, which shows for one do tankering and at what percentage level. This is illustrated in Figure 9, which shows for do tankering and at what percentage level. This is illustrated in Figure 9, which shows for specific aircraft model the percentage of fuel tankering possible as a function of the flight one specific aircraft model the percentage of fuel tankering possible as a function of the one specific aircraft model the percentage of fuel tankering possible as a function of the distance in NM and the percentage of additional fuel burnt. flight distance in NM and the percentage of additional fuel burnt. flight distance in NM and the percentage of additional fuel burnt. Figure 9. % of extra fuel burn as a function of % of tankering and distance flown for a specific aircraft Figure 9. % of extra fuel burn as a function of % of tankering and distance flown for a specific Figure 9. % of extra fuel burn as a function of % of tankering and distance flown for a specific aircraft model. mod aircraft el. model. Once the percentage of tankering capacity for this aircraft model for several theoret- Once the percentage of tankering capacity for this aircraft model for several theoretical Once the percentage of tankering capacity for this aircraft model for several theoret- ical distance flown are obtained, they have been applied to the real traffic in ECAC distance flown are obtained, they have been applied to the real traffic in ECAC grouped by ical distance flown are obtained, they have been applied to the real traffic in ECAC grouped by distance flown as illustrated in Figure 10. distance flown as illustrated in Figure 10. grouped by distance flown as illustrated in Figure 10. Figure Figure 10. 10. % % of of flight and % of flight and % of feasible feasible tankering per distance. tankering per distance. Figure 10. % of flight and % of feasible tankering per distance. 4.8. STEP 4: Estimate the Economic Opportunity of Tankering The fact that it is “technically possible” for a flight to make a full or partial tankering, does not mean that the airline operating that aircraft will decide to do so. Putting aside safety and special considerations at the destination airport (B), it was assumed in our model that this decision will be based on the cost savings that can be made, thanks to the difference in fuel prices negotiated at airports A and B. As can be seen in Figure 11, the average worldwide price of jet fuel is not constant. It is largely influenced by the crude oil price. Aerospace 2021, 8, x FOR PEER REVIEW 11 of 16 4.8. STEP 4: Estimate the Economic Opportunity of Tankering The fact that it is “technically possible” for a flight to make a full or partial tankering, does not mean that the airline operating that aircraft will decide to do so. Putting aside safety and special considerations at the destination airport (B), it was assumed in our model that this decision will be based on the cost savings that can be made, thanks to the difference in fuel prices negotiated at airports A and B. Aerospace 2021, 8, 37 11 of 16 As can be seen in Figure 11, the average worldwide price of jet fuel is not constant. It is largely influenced by the crude oil price. Figure 11. Average world price of crude Oil and Jet Fuel (IATA index Platts; https://www.iata.org/en/publications/eco- Figure 11. Average world price of crude Oil and Jet Fuel (IATA index Platts; https://www.iata.org/en/publications/ nomics/fuel-monitor/). economics/fuel-monitor/). In addition, the following factors influence also the price of jet fuel in each airport: In addition, the following factors influence also the price of jet fuel in each airport: ● Country; Country; ● Taxes (Fuel taxes in some ECAC country only for domestic flights), and refining costs; Taxes (Fuel taxes in some ECAC country only for domestic flights), and refining costs; ● Negotiation period; Negotiation period; ● Profit, quantities, and supply competition at airports; Profit, quantities, and supply competition at airports; ● Distribution technique; Distribution technique; ● Purchasing power and size of the aircraft operator’s fleet. Purchasing power and size of the aircraft operator ’s fleet. Generally, each airline negotiates, with a fuel provider, a fuel price at each airport it Generally, each airline negotiates, with a fuel provider, a fuel price at each airport it serves for an agreed duration. serves for an agreed duration. In addition, most airlines protect themselves against major fluctuations in fuel prices In addition, most airlines protect themselves against major fluctuations in fuel prices for the next six months to two years by using various hedging strategies and instruments. for the next six months to two years by using various hedging strategies and instruments. However However, , “h “hedging” edging” h has as no no s significant ignificant ef effect fect on on ex existing isting fuel pr fuel price ice d dififer fference encess between between airports, airports, and and could could only only m mar arg ginally inally red reduce uce the benef the benefit it of of tankering tankering [1 [133,14 ,14].]. Airlines Airlines ne negotiated gotiated ffuel uel pri prices ces are ar comm e commer ercial cially ly sens sensitive itive datdata a and and must must rema remain in con- confidential. fidential. For For this r this eason, the values reason, the values presented on presented the on map the (Figur map (Figur e 12) are e 12 aver ) arag e averaged ed values values calculated from the fuel prices negotiated by the airlines for which we were able to calculated from the fuel prices negotiated by the airlines for which we were able to obtain obtain this information. Nevertheless, it shows that there are large differences between fuel this information. Nevertheless, it shows that there are large differences between fuel prices at airports, e.g., Fuel price at Amsterdam (purple dot, so 0%) is among the cheapest prices at airports, e.g., Fuel price at Amsterdam (purple dot, so 0%) is among the cheapest in Europe. Fuel price at Ibiza and Hamburg or Oslo (yellow dots) is 30% more expensive in Europe. Fuel price at Ibiza and Hamburg or Oslo (yellow dots) is 30% more expensive than the cheapest airports, such as Amsterdam. Fuel price at Heathrow (light cyan dot) is than the cheapest airports, such as Amsterdam. Fuel price at Heathrow (light cyan dot) is 20%more expensive than the cheapest airports, such as Amsterdam, but 20% cheaper than Glasgow (red dot, 40%). In this study, we considered that each tonne of CO emitted required the purchase of CO allowances, which, as explained in STEP 1, is not the case. This cost is deducted from the benefit of doing tankering. Aerospace 2021, 8, x FOR PEER REVIEW 12 of 16 Aerospace 2021, 8, x FOR PEER REVIEW 12 of 16 20%more expensive than the cheapest airports, such as Amsterdam, but 20% cheaper than Glasgow (red dot, 40%). Aerospace 2021, 8, 37 20%more expensive than the cheapest airports, such as Amsterdam, but 20% cheaper than 12 of 16 Glasgow (red dot, 40%). Figure 12. Illustrative fuel price difference at airports. In this study, we considered that each tonne of CO2 emitted required the purchase of CO2 allow Figure 12. ances, wh Illustrative fu ich, as expla el pric ined e diff in erence at STEP 1, airports. is not the case. This cost is deducted from Figure 12. Illustrative fuel price difference at airports. the benefit of doing tankering. In this study, we considered that each tonne of CO2 emitted required the purchase of Figure 13 shows the net savings that could be achieved according to different percent- Figure 13 shows the net savings that could be achieved according to different percent- CO ages 2 allow of fuel anc tankering es, which, and as dif expla ferent ined fuel in price STEP for 1, is a not 600 t NM he cflight. ase. Thi Itsmust cost is be ded noted ucted from that this ages of fuel tankering and different fuel price for a 600 NM flight. It must be noted that the benefit o figure is simplified f doing t while anker in ing. the real processing there was a 10% step for every partial fuel this figure is simplified while in the real processing there was a 10% step for every partial tankering and real fuel price difference from some airlines. In the figure, it can be seen that Figure 13 shows the net savings that could be achieved according to different percent- fuel tankering and real fuel price difference from some airlines. In the figure, it can be seen age theseconomic of fuel tanker advant ingage and of di fuel fferent tankering fuel price is not foralways a 600 N possible. M flight.For It must differ be ences notein d t fuel hat that the economic advantage of fuel tankering is not always possible. For differences in tprices his figbetween ure is simpli airports fied whi (A and le inB) thof e re 2al and processin 5% theg benefi there was ts do a not 10% step for reach the 30 ev ery partial threshold. fuel prices between airports (A and B) of 2 and 5% the benefits do not reach the 30€ thresh- For a fuel price difference of 10% and for tankering from 40 to 100% the cost savings range fuel tankering and real fuel price difference from some airlines. In the figure, it can be seen old. For a fuel price difference of 10% and for tankering from 40 to 100% the cost savings from 44.4 to 94.9 . At a fuel price difference of 20% and tankering from 20 to 100% the cost that the economic advantage of fuel tankering is not always possible. For differences in range from 44.4 to 94.9€. At a fuel price difference of 20% and tankering from 20 to 100% savings range from 66.5 to 292.5 . fuel prices between airports (A and B) of 2 and 5% the benefits do not reach the 30€ thresh- the cost savings range from 66.5 to 292.5€. old. For a fuel price difference of 10% and for tankering from 40 to 100% the cost savings range from 44.4 to 94.9€. At a fuel price difference of 20% and tankering from 20 to 100% the cost savings range from 66.5 to 292.5€. Figure 13. Net saving and airport fuel price difference vs % of fuel tankering for a 600 NM flight. Figure 13. Net saving and airport fuel price difference vs % of fuel tankering for a 600 NM flight. Finally, by applying the Steps 2, 3, and 4 described above to all ECAC flights and Figure 13. Net saving and airport fuel price difference vs % of fuel tankering for a 600 NM flight. aircraft models considered in the simulations, the following results were obtained: As indicated in the Table 1 fuel tankering could result in a net saving of 265 M  per year for the airlines, but would generate 286,000 additional tonnes of fuel burnt (equivalent Aerospace 2021, 8, x FOR PEER REVIEW 14 of 17 Finally, by applying the Steps 2, 3, and 4 described above to all ECAC flights and aircraft models considered in the simulations, the following results were obtained: Table 1. Evaluated Net savings due to tankering versus Extra CO2 emitted. Aerospace 2021, 8, 37 13 of 16 Extra fuel burnt Cost to transport Extra CO2 Cost of purchasing Net saving = Tankering (tonnes/year) extra fuel emitted CO2 allowances saving - [Extra fuel + CO2 to 0.54% of ECAC jet fuel used) and 901,000 tonnes of CO emissions in the ECAC area (M€/year) (tonnes/year) (M€/year) cost] (M€/year) per year. Table 1. Evaluated Net savings due to tankering versus Extra CO emitted. Full tankering 160,000 88 504,000 10 217 Net Saving = Cost of Cost to Transport Extra CO Tankering Saving Partial tankering 126,000 69 397,000 8 48 Extra Fuel Burnt Purchasing CO Extra Fuel Emitted [Extra Fuel + (tonnes/year) Allowances (M /year) (tonnes/year) CO Cost] (M /year) (M /year) Total tankering 286,000 157 901,000 18 265 Full tankering 160,000 88 504,000 10 217 As indicated in the Table 1 fuel tankering could result in a net saving of 265 M€ per Partial tankering 126,000 69 397,000 8 48 year for the airlines, but would generate 286,000 additional tonnes of fuel burnt (equiva- Total tankering 286,000 157 901,000 18 265 lent to 0.54% of ECAC jet fuel used) and 901,000 tonnes of CO2 emissions in the ECAC area per year. Figure 14 shows that on the short and medium-haul fleet, the percentage of flights that Figure 14 shows that on the short and medium-haul fleet, the percentage of flights that could perform full fuel tankering decreases with the distance to be flown. This is mainly could perform full fuel tankering decreases with the distance to be flown. This is mainly due to the fact that as the distance to be flown increases, the aircraft has to carry much more due to the fact that as the distance to be flown increases, the aircraft has to carry much fuel from the departure airport (Airport A), therefore increasing its landing weight at the more fuel from the departure airport (Airport A), therefore increasing its landing weight destination airport (Airport B). When this landing weight exceeds the certified Maximum at the destination airport (Airport B). When this landing weight exceeds the certified Max- Landing Weight, full fuel tankering is not possible anymore. Partial tankering in turn takes imum Landing Weight, full fuel tankering is not possible anymore. Partial tankering in over until itself reaches its operational limit, for the same reasons, at more than 1500 NM. turn takes over until itself reaches its operational limit, for the same reasons, at more than Besides, it is obvious that the difference in fuel price has also a certain influence. 1500 NM. Besides, it is obvious that the difference in fuel price has also a certain influence. Figure 14. % of flights which could exercise fuel tankering (and save money by doing so), per distance flown. Figure 14. % of flights which could exercise fuel tankering (and save money by doing so), per distance flown. Figure 15 shows that distance matters, the longer the distance to be covered, the more Figure 15 shows that distance matters, the longer the distance to be covered, the more fuel needs to be tankered, leading to an increase in extra fuel burn. It should be noted that fuel needs to be tankered, leading to an increase in extra fuel burn. It should be noted that doubling the distance travelled results in more than doubling the fuel needed to carry this doubling the distance travelled results in more than doubling the fuel needed to carry this extra extra fuel fuel, , a and nd thus the resul thus the resulting ting emissions. emissions. Figure 16 shows the distribution of the 160,000 tonnes of additional fuel burnt (505,000 tonnes of CO ) due to full fuel tankering and the 126,000 tonnes of additional fuel burnt (397,000 tonnes of CO ) due to partial tankering per distance flown. It clearly shows that the partial tankering is mainly performed over long distances in ECAC and represents a significant part of the extra fuel burnt. Although only 4.5% of flights perform partial tankering, they account for nearly half of the CO emissions (44%) due to this practice. 2 Aerospace 2021, 8, x FOR PEER REVIEW 15 of 17 Aerospace 2021, 8, x FOR PEER REVIEW 15 of 17 Aerospace 2021, 8, 37 14 of 16 Figure 15. Extra fuel burn per distance flown. Figure 16 shows the distribution of the 160,000 tonnes of additional fuel burnt (505,000 tonnes of CO2) due to full fuel tankering and the 126,000 tonnes of additional fuel burnt (397,000 tonnes of CO2) due to partial tankering per distance flown. It clearly shows that the partial tankering is mainly performed over long distances in ECAC and represents a significant part of the extra fuel burnt. Although only 4.5% of flights perform partial Figure 15. Extra fuel burn per distance flown. Figure 15. Extra fuel burn per distance flown. tankering, they account for nearly half of the CO2 emissions (44%) due to this practice. Figure 16 shows the distribution of the 160,000 tonnes of additional fuel burnt (505,000 tonnes of CO2) due to full fuel tankering and the 126,000 tonnes of additional fuel burnt (397,000 tonnes of CO2) due to partial tankering per distance flown. It clearly shows that the partial tankering is mainly performed over long distances in ECAC and represents a significant part of the extra fuel burnt. Although only 4.5% of flights perform partial tankering, they account for nearly half of the CO2 emissions (44%) due to this practice. Figure 16. Tonnes of extra fuel burn per distance flown. Figure 16. Tonnes of extra fuel burn per distance flown. 5. Conclusions 5. Conclusions As aviation is a very competitive market, airlines must do everything possible to As aviation is a very competitive market, airlines must do everything possible to minimize their operating costs, in particular regarding fuel cost, which represents 17 to minimize their operating costs, in particular regarding fuel cost, which represents 17 to 25% of their operating expenses [1]; this goes even up to 50% for some low-cost carriers. 25% of their operating expenses [1]; this goes even up to 50% for some low-cost carriers. Figure 16. Tonnes of extra fuel burn per distance flown. Consequently, airlines are using tools for identifying the value of performing fuel tanker- Consequently, airlines are using tools for identifying the value of performing fuel tankering, ing, a practice whereby an aircraft carries more fuel than required for its flight in order to a practice whereby an aircraft carries more fuel than required for its flight in order to save 5. Conclusions save costs. However, fuel tankering is not without environmental consequences, as the costs. However, fuel tankering is not without environmental consequences, as the more more fuel an aircraft carries, the more fuel it burns and the more CO2 it emits. The use of As aviation is a very competitive market, airlines must do everything possible to fuel an aircraft carries, the more fuel it burns and the more CO it emits. The use of fuel minimize their operating costs, in particular regarding fuel cost, which represents 17 to tankering by long-haul flights will be the subject of a future study. This study is limited to 25% of their operating expenses [1]; this goes even up to 50% for some low-cost carriers. flights up to 1500 and 2500 NM, corresponding mainly to short and medium-haul flights. Consequently, airlines are using tools for identifying the value of performing fuel tanker- It is estimated that fuel tankering could result in a net saving of 265 M  per year for the ing, a practice whereby an aircraft carries more fuel than required for its flight in order to airlines, but would generate 286,000 additional tonnes of fuel burnt (equivalent to 0.54% of save costs. However, fuel tankering is not without environmental consequences, as the ECAC jet fuel used) and 901,000 tonnes of CO emissions in the ECAC area per year. This is more fuel an aircraft carries, the more fuel it burns and the more CO2 it emits. The use of equivalent to about 2800 round-trips between Paris and New York or the annual emissions Aerospace 2021, 8, 37 15 of 16 of a European city of 100,000 inhabitants. This is a substantial economic benefit but also a significant environmental impact. Consequently, fuel tankering could offset the benefit of initiatives to save fuel and reduce aviation CO emissions. At a time when aviation is challenged for its contribution to climate change, a practice, such as fuel tankering, that generates significant additional CO emissions is questionable. Unfortunately, the COVID19 crisis has created such economic pressure that airlines have intensified the practice of fuel tankering since then, as reported by some pilots. Author Contributions: All the authors contributed equally to this work. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data used to produce this analysis are EUROCONTROL data and are not available in the public domain. In particular, negotiated fuel prices at the airports used in this study remain confidential. Acknowledgments: This study was carried out with the aim of raising awareness of the considerable environmental impact of a practice such as fuel tankering. It was carried out independently, but required the collection of commercially sensitive information, which we had to anonymize. The results of this study were published in EUROCONTROL’s first “Think Paper”, and subsequently picked up in many newspapers, news feeds and other media [15,16]. Following its publication, a number of airlines had begun to reflect on reducing or even abandoning this economic practice. The authors would like to express their deep gratitude to all colleagues who were directly or indirectly involved in this study, and to the EUROCONTROL top management who had the courage to make it public. Conflicts of Interest: There are no conflicts of interest whatsoever. References 1. Kumar, N.; Frolik, P.; Joshi, G.; Ramadugu, H. World Air Transport Statistics; IATA: Montreal, QC, Canada, 2017. 2. ICAO. 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Ryanair ’s O’Leary Says Happy to Continue as CEO for 2 to 3 Years. Available online: https: //www.youtube.com/watch?v=PgpwYeEj5Roat0\T1\textquoteright57\T1\textquotedblright (accessed on 8 October 2020). 15. BBC Panorama. Can Flying Go Green? Available online: https://www.youtube.com/watch?v=mPhOS4uXkmM (accessed on 8 October 2020). 16. Rowlatt, J. Climate change: British Airways Reviews ‘Fuel-Tankering’ over Climate Concerns. BBC News. 11 November 2019. Available online: https://www.bbc.com/news/science-environment-50365362 (accessed on 8 October 2020).

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AerospaceMultidisciplinary Digital Publishing Institute

Published: Jan 31, 2021

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