[aidenn0]

It seems like if the fuel costs were to go down, you'd want a larger plane, since crew and maintenance costs would make up a larger fraction of the costs?

[edit]

Looks like the site answers this; reduced maintenance costs when not having a high-temperature turbine are predicted to lead to similar CASM as a 737 despite being about 1/3 the seats.

[stuart8ol]

I think that is a fair statement. You also have to factor in the capital costs, the aircraft purchase price per seat typically increases with aircraft size so it comes down to the balance there, between that cost increasing and other costs decreasing. The scales can tip either way depending on the circumstances. For a 737, we have that capital costs contribute about 40% of the CASM, whereas Crew is 4% and Maintenance is 16%. In conventional aircraft, the efficiency of larger engines really vs smaller ones really push towards larger aircraft.