[krisoft]

Developing an airplane, I would guess.

[rabidonrails]

I heard it was the little bags of peanuts :P

[foobarqux]

I meant operating costs.

[jonknee]

Yes, fuel is the major operating cost of an airliner...

[mnw21cam]

Similarly, for a jet engine, the fuel burned in it accounts for 99% of the environmental impact.