Fuel economy in aircraft

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A Boeing 747 in cruise flight: Aircraft like this burn jet fuel.

Aircraft must consume fuel to supply the energy needed to move the vehicles and their passengers. Fuel economy is a measure of how much fuel an aircraft needs to operate, and can be expressed in several ways, for example by the liters of fuel consumed per passenger per kilometer. Aerodynamic drag, which exerts a force on the aircraft in the opposite direction from the velocity, is a principal determinant of energy consumption in aircraft because they operate at such high speeds.

Factors in aircraft fuel economy[edit]

Each model of aircraft has a maximum range speed for a given total load (fuel plus payload), which is the speed at which it is most fuel efficient.[1] Flying slower or faster than this optimum speed increases fuel consumption per mile flown. There is an optimum speed for efficiency because the component of drag resulting from airframe skin friction against the air increases at a square function of air speed, but the drag resulting from generating lift decreases with air speed. (These are technically called parasitic drag and induced drag, respectively.)[1] The desirability of a low maximum range speed to reduce environmental and climate impacts is at odds in aircraft design with the benefit from the revenue generated by making the design speed higher thereby increasing the passenger miles flown per day.[2]

Aircraft weight is also a factor in fuel economy, because more lift-generating drag (induced drag) results as weight increases. If the airframe weight is reduced, engines that are smaller and lighter can be used, and for a given range the fuel capacity can be reduced. Thus some weight savings can be compounded for an increase in fuel efficiency. A rule-of-thumb being that a 1% weight reduction corresponds to around a 0.75% reduction in fuel consumption.[3]

Flight altitude affects engine efficiency. Jet-engine efficiency increases at altitude up to the tropopause, the temperature minimum of the atmosphere; at lower temperatures, the engine efficiency is higher.[1] Jet engine efficiency is also increased at high speeds, but above about Mach 0.85 the aerodynamic drag on the airframe overwhelms this effect.

Above that speed, shockwaves begin to form that greatly increase drag. For supersonic flight (Mach 1.0 or higher), fuel consumption is increased tremendously.

Changes in commercial aircraft fuel economy since the 1950s[edit]

Although modern jet aircraft have twice the fuel efficiency of the earliest jet airliners, [4] they are only slightly more fuel efficient than the latest piston engine airliners of the late 1950s such as the Lockheed L-1649 Starliner and Douglas DC-7.[2] Nonetheless, jets have about twice the cruise speed. The early jet airliners were designed at a time when air crew labor costs were higher relative to fuel costs than today. Despite the high fuel consumption, because fuel was inexpensive in that era the higher speed resulted in favorable economical returns since crew costs and amortization of capital investment in the aircraft could be spread over more seat miles flown per day.[5]

Today's turboprop airliners have better fuel efficiency than current jet airliners, in part because of their lower cruising speed and propellers that are more efficient than those of the 1950s-era piston-powered airlines.[6] Among major airlines, those with turboprop equipped regional carrier subsidiaries typically rank high in overall fleet fuel efficiency. For example, although Alaska Airlines scored at the top of a 2011-2012 fuel efficiency ranking, if its regional carrier—turbo-prop equipped Horizon Air—were dropped from the consideration, the airline's ranking would be lower.[6]

Jet aircraft efficiency[edit]

Jet aircraft efficiency is improving: Between 1960 and 2000 there was a 55% overall fuel efficiency gain (if one were to consider the Boeing 707 as the base case).[2] Most of the improvements in efficiency were gained in the first decade when jet craft first came into widespread commercial use. Between 1971 and 1998 the fleet-average annual improvement per available seat-kilometre was estimated at 2.4%. Concorde the supersonic transport managed about 17 passenger-miles to the Imperial gallon, which is 16.7 L/100 km per passenger; similar to a business jet, but much worse than a subsonic turbofan aircraft. Airbus states a fuel rate consumption of their A380 at less than 3 L/100 km per passenger (78 passenger-miles per US gallon).[7]

Weight effect[edit]

As over 80% of the fully laden take-off weight of a modern aircraft such as the Airbus A380 is craft and fuel, there remains considerable room for future improvements in fuel efficiency. The weight of an aircraft can be reduced by using light-weight materials such as titanium, carbon fiber and other composite plastics. Expensive materials may be used, if the reduction of mass justifies the price of materials through improved fuel efficiency. The improvements achieved in fuel efficiency by mass reduction, reduce the amount of fuel an aircraft must carry. This further reduces the mass of the aircraft, and therefore provides further gains in fuel efficiency. For example, the Airbus A380 design includes multiple light-weight materials. The Boeing 787 Dreamliner was the first major commercial airplane to have a composite fuselage, composite wings, and use composites in most other airframe components.[8]

Very long non-stop flights suffer from the weight penalty of the large quantity of fuel required, limiting the number of available seats to compensate. For such flights, the critical fiscal factor is the quantity of fuel burnt per seat-nautical mile.[9] For these reasons the world's longest commercial flights were cancelled circa 2013. An example is Singapore Air's former New York to Singapore flight, which could carry only 100 passengers (all business class) on the 10,300 mile flight. According to an industry analyst, "It [was] pretty much a fuel tanker in the air."[10]

Aerodynamics[edit]

Main article: Lift-to-drag ratio

Airbus has showcased wingtip devices (sharklets or winglets) that can achieve 3.5 percent reduction in fuel consumption.[11][12] There are wingtip devices on the Airbus A380. Further developed Minix winglets have been said to offer 6 percent reduction in fuel consumption.[13] Winglets at the tip of an aircraft wing, can be retrofitted to any airplane, and smooths out the wing-tip vortex, reducing the aircraft's wing drag.[13]

NASA and Boeing are conducting tests on a 500 lb (230 kg) "blended wing" aircraft. This design provides greater fuel efficiency, since the whole craft produces lift, not just the wings.[14] The blended wing body (BWB) concept offers advantages in structural, aerodynamic and operating efficiencies over today's more conventional fuselage-and-wing designs. These features translate into greater range, fuel economy, reliability and life cycle savings, as well as lower manufacturing costs.[15][16] NASA has created a cruise efficient STOL (CESTOL) concept.

Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research (IFAM) have researched a shark skin imitating paint that would reduce drag through a riblet effect.[17] Aircraft is a major potential application for new technologies such as aluminium metal foam and nanotechnology such as the shark skin imitating paint.

Fuel consumption factors[edit]

To save fuel, Simon Weselby presented the following measures while flying, in his example of an A330 flying 4,600 kilometres (2,900 mi):[18]

  • direct routing: 40 km (25 mi) less distance saves 190 kg (419 lb) fuel
  • vertical flight profile optimization: fly 600 m (1,969 ft) below optimum altitude, 600 kg (1,323 lb) more fuel consumed
  • cruising speed: 0.01 mach above optimum, 800 kg (1,764 lb) more fuel consumed
  • aircraft weight: 1,000 kg (2,205 lb) more fuel on board, 150 kg (331 lb) more fuel consumed. 100 litres (22 imp gal; 26 US gal) of unused potable water, 15 kg (33 lb) more fuel consumed.

Also operational procedures can save fuel:[18]

  • 10 minutes less APU use, 35 kg (77 lb) fuel saved
  • reduced flap approach, 15 kg (33 lb) fuel saved
  • reduced thrust reversal, 30 kg (66 lb) fuel saved

Maintenance saves fuel as well:[18]

  • no engine wash schedule: 100 kg (220 lb) more fuel consumed
  • slat rigging, 5 mm (0.20 in) gap, 50 kg (110 lb) more fuel consumed
  • spoiler rigging, 10 mm (0.39 in) gap, 40 kg (88 lb) more fuel consumed
  • damaged door seal, 15 kg (33 lb) more fuel consumed

Propellers versus jets[edit]

Propfans are a more fuel efficient technology than jets or turboprops, but turboprops have an optimum speed below about 450 mph (700 km/h).[19] This speed is less than used with jets by major airlines today. However, the decrease in speed reduces drag. With the current [needs update] high price for jet fuel and the emphasis on engine/airframe efficiency to reduce emissions, there is renewed interest in the propfan concept for jetliners that might come into service beyond the Boeing 787 and Airbus A350XWB. For instance, Airbus has patented aircraft designs with twin rear-mounted counter-rotating propfans.[20] NASA has conducted an Advanced Turboprop Project (ATP), where they researched a variable pitch propfan that produced less noise and achieved high speeds.

For private aircraft in general aviation, the current record is 37 km/kg fuel or 3.7 L/100 km in a Monnett Sonerai.[21]

Related to fuel efficiency is the impact of aviation emissions on climate.

Range[edit]

For very long haul flights, the airplane is heavier to transport additional fuel, leading to a higher fuel consumption. Above a certain distance, it becomes more fuel efficient to make a halfway stop to refuel even if it leads to an additional less efficient descent and climb. For example, for a Boeing 777-300 the tipping point is at 3,000 nautical miles (5,600 km) : it is more fuel efficient to make a non-stop flight below this distance and to make a stop above.[22]

Boeing 777-224 fuel burn per distance against range

Airline fuel efficiency[edit]

Fuel economy in air transport comes from aircraft fuel efficiency combined with airlines efficiency : seating configuration, passenger load factor and air cargo. For instance, over the transatlantic route, the most active intercontinental market, in 2014 the average fuel consumption was 32 pax-km per L - 3.13 litres per 100 kilometres (75 mpg-US) per passenger. The most fuel efficient airline was Norwegian Air Shuttle with 40 pax-km/L - 2.5 litres per 100 kilometres (94 mpg-US) per passenger, thanks to its fuel efficient Boeing 787-8, a high 86% passenger load factor and a high density of 1.18 seat/m² due to a low 11% premium seating. On the other side, the least efficient was British Airways at 27 pax-km/L - 3.7 litres per 100 kilometres (64 mpg-US) per passenger, using fuel inefficient Boeing 747-400s with a low density of 0.79 seat/m² due to a high 24% premium seating, in spite of a high 83% load factor.[23]

Research projects such as Boeing's ecoDemonstrator program have sought to identify ways of improving the fuel economy of commercial aircraft operations. The U.S. government has encouraged such research through grant programs, including the FAA's Continuous Lower Energy, Emissions and Noise (CLEEN) program, and NASA's Environmentally Responsible Aviation (ERA) Project.[citation needed]

Example Values[edit]

Turboprop[edit]

300 nautical miles (560 km) sector

model first flight seats Fuel burn Fuel per seat
ATR 42-500 1995 48 1.26 kg/km (4.5 lb/mi) 3.07 L/100 km (77 mpg-US)[24]
ATR 72-500 1997 70 1.42 kg/km (5.0 lb/mi) 2.47 L/100 km (95 mpg-US)[24]
Bombardier Dash 8 Q400 1998 78 2.16 kg/km (7.7 lb/mi) 3.38 L/100 km (70 mpg-US)[25]
Dornier 228 1981 19 0.94 kg/km (3.3 lb/mi) 6.06 L/100 km (38.8 mpg-US)[26]
Dornier 328 1991 30 1.10 kg/km (3.91 lb/mi) 4.51 L/100 km (52.2 mpg-US)[27]
Embraer Brasilia 1983 30 0.92 kg/km (3.3 lb/mi) 3.82 L/100 km (61.6 mpg-US)[28]
Pilatus PC-12 (500nm) 1991 9 0.41 kg/km (1.5 lb/mi) 5.66 L/100 km (41.6 mpg-US)[29]

Regional[edit]

model first flight seats sector Fuel burn Fuel efficiency per seat
Airbus A319neo 2015 144 600 nmi (1,100 km) 2.93 kg/km (10.4 lb/mi) 2.04 L/100 km (115 mpg-US)[30]
Airbus A319neo 2015 124 660 nmi (1,220 km) 2.85 kg/km (10.1 lb/mi) 2.82 L/100 km (83.5 mpg-US)[31]
Airbus A320neo 2015 154 660 nmi (1,220 km) 2.82 kg/km (10 lb/mi) 2.25 L/100 km (104.7 mpg-US)[31]
Airbus A321neo 2015 192 660 nmi (1,220 km) 3.35 kg/km (11.9 lb/mi) 2.19 L/100 km (107.4 mpg-US)[31]
Boeing 737-300 1984 126 507 nmi (939 km) 3.55 kg/km (12.6 lb/mi) 3.46 L/100 km (68 mpg-US)[32]
Boeing 737-600 1998 110 500 nmi (930 km) 3.16 kg/km (11.2 lb/mi) 3.5 L/100 km (67 mpg-US)[33]
Boeing 737-700 1997 126 500 nmi (930 km) 3.21 kg/km (11.4 lb/mi) 3.11 L/100 km (76 mpg-US)[33]
Boeing 737 MAX 7 2017 128 660 nmi (1,220 km) 2.90 kg/km (10.3 lb/mi) 2.77 L/100 km (84.8 mpg-US)[31]
Boeing 737 MAX 7 2017 144 600 nmi (1,100 km) 2.94 kg/km (10.4 lb/mi) 2.04 L/100 km (115 mpg-US)[30]
Boeing 737-800 1997 162 500 nmi (930 km) 3.59 kg/km (12.7 lb/mi) 2.7 L/100 km (87 mpg-US)[33]
Boeing 737 MAX 8 2017 166 660 nmi (1,220 km) 3.07 kg/km (10.9 lb/mi) 2.28 L/100 km (103.2 mpg-US)[31]
Boeing 737-900ER 2006 180 500 nmi (930 km) 3.83 kg/km (13.6 lb/mi) 2.59 L/100 km (91 mpg-US)[33]
Boeing 737 MAX 9 2017 180 660 nmi (1,220 km) 3.35 kg/km (11.9 lb/mi) 2.3 L/100 km (103 mpg-US)[31]
Bombardier CRJ1000 2009 100 500 nmi (930 km) 2.73 kg/km (9.7 lb/mi) 3.33 L/100 km (71 mpg-US) [34]
Bombardier CSeries 100 2013 115 600 nmi (1,100 km) 2.46 kg/km (8.7 lb/mi) 2.14 L/100 km (110 mpg-US)[30]
Bombardier CSeries 300 2015 140 600 nmi (1,100 km) 2.68 kg/km (9.5 lb/mi) 1.92 L/100 km (123 mpg-US)[30]
Embraer E-Jet E2-175 2020 88 600 nmi (1,100 km) 2.11 kg/km (7.5 lb/mi) 2.4 L/100 km (98 mpg-US)[30]
Embraer E-Jet E2-190 2018 106 600 nmi (1,100 km) 2.45 kg/km (8.7 lb/mi) 2.32 L/100 km (101 mpg-US)[30]
Embraer E-Jet E2-195 2019 132 600 nmi (1,100 km) 2.67 kg/km (9.5 lb/mi) 2.03 L/100 km (116 mpg-US)[30]
Embraer E-Jet-190 2002 98 500 nmi (930 km) 2.98 kg/km (10.6 lb/mi) 3.81 L/100 km (61.7 mpg-US)[35]
Sukhoi SSJ100 2008 98 500 nmi (930 km) 2.81 kg/km (10.0 lb/mi) 3.59 L/100 km (65.5 mpg-US)[35]

Short haul[edit]

1,000 nautical miles (1,900 km) sector

model first flight seats Fuel Burn Fuel efficiency per seat
Airbus A319 1995 124 2.99 kg/km (10.6 lb/mi) 2.95 L/100 km (80 mpg-US)[36]
Airbus A319Neo 2015 136 2.46 kg/km (8.73 lb/mi) 1.93 L/100 km (122 mpg-US)[37]
Airbus A320 1987 150 3.18 kg/km (11.3 lb/mi) 2.61 L/100 km (90 mpg-US)[36]
Airbus A321-200 1996 180 3.66 kg/km (13 lb/mi) 2.5 L/100 km (94 mpg-US)[36]
Airbus A330-200 1997 293 5.66 kg/km (20.09 lb/mi) 2.37 L/100 km (99 mpg-US)[36]
Boeing 737-600 1998 110 2.78 kg/km (9.9 lb/mi) 3.08 L/100 km (76 mpg-US)[33]
Boeing 737-700 1997 126 2.82 kg/km (10.0 lb/mi) 2.73 L/100 km (86 mpg-US)[33]
Boeing 737-700 1997 128 2.83 kg/km (10.05 lb/mi) 2.71 L/100 km (87 mpg-US)[36]
Boeing 737 MAX-7 2017 140 2.55 kg/km (9.04 lb/mi) 1.94 L/100 km (121 mpg-US)[37]
Boeing 737-800 1997 162 3.17 kg/km (11.2 lb/mi) 2.38 L/100 km (99 mpg-US)[33]
Boeing 737-800 1997 160 3.50 kg/km (12.41 lb/mi) 2.68 L/100 km (88 mpg-US)[36]
Boeing 737-800W 1997 162 3.18 kg/km (11.3 lb/mi) 2.39 L/100 km (98 mpg-US)[38]
Boeing 737 MAX-8 2017 162 2.71 kg/km (9.6 lb/mi) 2.04 L/100 km (115 mpg-US)[38]
Boeing 737-900ER 2006 180 3.42 kg/km (12.1 lb/mi) 2.32 L/100 km (101 mpg-US)[33]
Boeing 737-900ERW 2006 180 3.42 kg/km (12.1 lb/mi) 2.31 L/100 km (102 mpg-US)[38]
Boeing 737 MAX-9 2017 180 2.91 kg/km (10.3 lb/mi) 1.97 L/100 km (119 mpg-US)[38]
Boeing 757-200 1982 190 4.67 kg/km (16.57 lb/mi) 3.02 L/100 km (78 mpg-US)[36]
Bombardier CS300 2015 135 2.34 kg/km (8.3 lb/mi) 1.85 L/100 km (127 mpg-US)[37]

Medium haul[edit]

Around 3,000 nautical miles (5,600 km) sector, typically transatlantic, e.g. New York JFK - London-Heathrow [39]

model first flight seats sector Fuel burn Fuel per seat
Airbus A321NeoLR 2016 154 3,400 nmi (6,300 km)) 2.99 kg/km (10.6 lb/mi) 2.41 L/100 km (98 mpg-US)[40]
Airbus A330-200 1997 241 3,000 nmi (5,600 km) 6.03 kg/km (21.4 lb/mi) 3.11 L/100 km (76 mpg-US)[41]
Airbus A330-300 1992 262 3,000 nmi (5,600 km) 6.28 kg/km (22.3 lb/mi) 2.98 L/100 km (79 mpg-US)[41]
Airbus A330neo-900 2016 310 3,350 nmi (6,200 km) 6.03 kg/km (21.4 lb/mi) 2.42 L/100 km (97 mpg-US)[42]
Airbus A340-300 1992 262 3,000 nmi (5,600 km) 6.85 kg/km (24.3 lb/mi) 3.25 L/100 km (72 mpg-US)[41]
Boeing 747-8 2011 467 3,000 nmi (5,600 km) 9.9 kg/km (35 lb/mi) 2.59 L/100 km (91 mpg-US)[43]
Boeing 737 MAX-8 2017 168 3,400 nmi (6,300 km)) 2.86 kg/km (10.1 lb/mi) 2.13 L/100 km (110 mpg-US)[44]
Boeing 737 MAX-9 2017 144 3,400 nmi (6,300 km)) 2.91 kg/km (10.3 lb/mi) 2.51 L/100 km (94 mpg-US)[40]
Boeing 757-200W 1981 158 3,400 nmi (6,300 km)) 3.79 kg/km (13.4 lb/mi) 2.99 L/100 km (79 mpg-US)[40]
Boeing 767-200ER 1984 181 3,000 nmi (5,600 km)) 4.83 kg/km (17.1 lb/mi) 3.32 L/100 km (71 mpg-US)[45]
Boeing 767-200ER 1984 193 3,400 nmi (6,300 km)) 5.01 kg/km (17.8 lb/mi) 3.23 L/100 km (73 mpg-US)[40]
Boeing 767-200ER 1984 224 3,000 nmi (5,600 km)) 4.93 kg/km (17.5 lb/mi) 2.74 L/100 km (86 mpg-US)[45]
Boeing 767-300ER 1988 218 3,000 nmi (5,600 km)) 5.39 kg/km (19.1 lb/mi) 3.07 L/100 km (77 mpg-US)[45]
Boeing 767-300ER 1988 269 3,000 nmi (5,600 km)) 5.51 kg/km (19.5 lb/mi) 2.55 L/100 km (92 mpg-US)[45]
Boeing 767-400ER 1999 245 3,000 nmi (5,600 km)) 5.78 kg/km (20.5 lb/mi) 2.93 L/100 km (80 mpg-US)[45]
Boeing 767-400ER 1999 304 3,000 nmi (5,600 km)) 5.93 kg/km (21.0 lb/mi) 2.42 L/100 km (97 mpg-US)[45]
Boeing 767-400ER 1999 304 3,265 nmi (6,047 km) 6.00 kg/km (21.3 lb/mi) 2.43 L/100 km (96.9 mpg-US)[32]
Boeing 777-200 1994 305 3,000 nmi (5,600 km) 6.83 kg/km (24.2 lb/mi) 2.73 L/100 km (86 mpg-US)[46]
Boeing 777-200ER 1996 301 3,000 nmi (5,600 km) 6.99 kg/km (24.8 lb/mi) 2.89 L/100 km (81 mpg-US)[41]
Boeing 777-300 1997 368 3,000 nmi (5,600 km) 7.88 kg/km (28.0 lb/mi) 2.61 L/100 km (90 mpg-US)[46]
Boeing 787-8 2009 291 3,400 nmi (6,300 km)) 5.26 kg/km (18.7 lb/mi) 2.26 L/100 km (104 mpg-US)[44]
Boeing 787-8 2009 238 3,400 nmi (6,300 km)) 5.11 kg/km (18.1 lb/mi) 2.67 L/100 km (88 mpg-US)[40]
Boeing 787-9 2013 304 3,350 nmi (6,200 km) 5.8 kg/km (21 lb/mi) 2.37 L/100 km (99 mpg-US)[42]

Long haul[edit]

Around 6,000 nautical miles (11,000 km) sector, typically transpacific, e.g. Hong kong international - San Francisco Intl[47]

model first flight seats sector Fuel burn Fuel per seat
Airbus A330-200 1997 241 6,000 nmi (11,000 km) 6.48 kg/km (23.0 lb/mi) 3.32 L/100 km (71 mpg-US)[41]
Airbus A330neo-800 2017 248 4,650 nmi (8,610 km) 5.52 kg/km (19.6 lb/mi) 2.75 L/100 km (86 mpg-US)[48]
Airbus A330neo-900 2017 300 4,650 nmi (8,610 km) 6.02 kg/km (21.4 lb/mi) 2.48 L/100 km (95 mpg-US)[48]
Airbus A340-300 1992 262 6,000 nmi (11,000 km) 7.41 kg/km (26.3 lb/mi) 3.49 L/100 km (67.4 mpg-US)[41]
Airbus A350-900 2013 315 4,972 nmi (9,208 km) 6.11 kg/km (21.7 lb/mi) 2.39 L/100 km (98 mpg-US)[42]
Airbus A350-900 2013 315 6,542 nmi (12,116 km) 7.07 kg/km (25.1 lb/mi) 2.86 L/100 km (82 mpg-US)[49]
Airbus A380 2005 525 7,200 nmi (13,300 km) 13.78 kg/km (48.9 lb/mi) 3.27 L/100 km (72 mpg-US)[50]
Airbus A380 2005 544 6,000 nmi (11,000 km) 13.78 kg/km (48.9 lb/mi) 3.16 L/100 km (74 mpg-US)[51]
Boeing 747-400 1988 416 6,000 nmi (11,000 km) 11.11 kg/km (39.4 lb/mi) 3.26 L/100 km (72 mpg-US)[52]
Boeing 747-8 2011 467 6,000 nmi (11,000 km) 10.54 kg/km (37.4 lb/mi) 2.75 L/100 km (86 mpg-US)[43]
Boeing 747-8 2011 405 7,200 nmi (13,300 km) 10.9 kg/km (39 lb/mi) 3.35 L/100 km (70 mpg-US)[50]
Boeing 777-200ER 1996 301 6,000 nmi (11,000 km) 7.51 kg/km (26.6 lb/mi) 3.08 L/100 km (76 mpg-US)[41]
Boeing 777-200ER 1996 301 6,000 nmi (11,000 km) 7.44 kg/km (26.4 lb/mi) 3.01 L/100 km (78 mpg-US)[46]
Boeing 777-200LR 2005 291 4,972 nmi (9,208 km) 7.66 kg/km (27.2 lb/mi) 3.25 L/100 km (72 mpg-US)[42]
Boeing 777-300ER 2003 365 6,000 nmi (11,000 km) 8.49 kg/km (30.1 lb/mi) 2.84 L/100 km (83 mpg-US)[46]
Boeing 777-300ER 2003 344 7,200 nmi (13,300 km) 8.58 kg/km (30.4 lb/mi) 3.11 L/100 km (76 mpg-US)[50]
Boeing 777-9X 2020 395 7,200 nmi (13,300 km) 9.04 kg/km (32.1 lb/mi) 2.85 L/100 km (83 mpg-US)[50]
Boeing 787-8 2011 243 4,650 nmi (8,610 km) 5.45 kg/km (19.3 lb/mi) 2.77 L/100 km (85 mpg-US)[48]
Boeing 787-9 2013 294 4,650 nmi (8,610 km) 5.93 kg/km (21.0 lb/mi) 2.49 L/100 km (94 mpg-US)[48]
Boeing 787-9 2013 304 4,972 nmi (9,208 km) 5.7 kg/km (20 lb/mi) 2.31 L/100 km (102 mpg-US)[42]
Boeing 787-9 2013 291 6,542 nmi (12,116 km) 7.18 kg/km (25.5 lb/mi) 3.14 L/100 km (75 mpg-US)[49]

For comparison, a Volvo Buses 9700 averages 0.41 litres per 100 kilometres (570 mpg-US) per seat for 63 seats.[53] In highway travel an average auto has the potential for 1.61 litres per 100 kilometres (146 mpg-US)[54] per seat (assuming 4 seats) and for a 5-seat 2014 Toyota Prius, 0.98 litres per 100 kilometres (240 mpg-US).[55] While this shows the capabilities of the vehicles, the load factors (percentage of seats occupied) may differ between personal use (commonly just the driver in the car) and societal averages for long-distance auto use, and among those of particular airlines.

References[edit]

  1. ^ a b "Drag". Skybrary. Retrieved June 8, 2014. 
  2. ^ a b c Peeters, P. M.; Middel, J.; Hoolhorst, A. (2005). "Fuel efficiency of commercial aircraft: An overview of historical and future trends" (PDF). National Aerospace Laboratory. Retrieved July 6, 2014. 
  3. ^ Barney L. Capehart (2007). Encyclopedia of Energy Engineering and Technology. 1. CRC Press. ISBN 978-0-8493-3653-9. 
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