The difference is just not worth it on a per passenger basis. I looked into this to answer another passing curiosity some months ago. For a thousand mile flight

The difference is just not worth it on a per passenger basis. I looked into this to answer another passing curiosity some months ago. For a thousand mile flight the cost per pound is about $0.05. Source: Based on this forum thread [1] the marginal cost per pound to fuel efficiency is about "0.0155 gallons per pound per 1,000 statute miles". Over a 737's life it may fly about 50 million miles [2]. Combining facts one and two results in a fuel consumption per marginal pound of 775 gallons. Current jet fuel prices are about $3.40 per gal [3]. [1] https://www.flyertalk.com/forum/travelbuzz/712294-anyone-kno https://www.flyertalk.com/forum/travelbuzz/712294-anyone-kno... [2] https://www.usatoday.com/story/travel/columnist/cox/2012/11/ https://www.usatoday.com/story/travel/columnist/cox/2012/11/... [3] https://www.iata.org/en/publications/economics/fuel-monitor/ https://www.iata.org/en/publications/economics/fuel-monitor/