<P> Airbus presented the following measures to save fuel, in his example of an A330 flying 2,500 nautical miles (4,600 km) like Bangkok - Tokyo: direct routing saves 190 kg (420 lb) fuel by flying 40 km (25 mi) less; 600 kg (1,300 lb) more fuel is consumed if flying 600 m (2,000 ft) below optimum altitude without vertical flight profile optimization; cruising 0.01 mach above optimum consumes 800 kg (1,800 lb) more fuel; 1,000 kg (2,200 lb) more fuel on board consumes 150 kg (330 lb) more fuel or 100 litres (22 imp gal; 26 US gal) of unused potable water consumes 15 kg (33 lb) more fuel . </P> <P> Operational procedures can save 35 kg (77 lb) fuel by using the APU 10 minutes less, 15 kg (33 lb) with a reduced flap approach and 30 kg (66 lb) with reduced thrust reversal . Maintenance saves fuel as well: 100 kg (220 lb) more fuel is consumed without an engine wash schedule; 50 kg (110 lb) with a 5 mm (0.20 in) slat rigging gap, 40 kg (88 lb) with a 10 mm (0.39 in) spoiler rigging gap, 15 kg (33 lb) with a damaged door seal . </P> <P> Modern jet aircraft have twice the fuel efficiency of the earliest jet airliners . Late 1950s piston airliners like the Lockheed L - 1049 Super Constellation and DC - 7 were 1% to 28% more energy intensive than 1990s jet airliners which cruise 40 to 80% faster . 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 . </P> <P> 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 . </P>

How much fuel does a a320 burn per hour