At current fuel prices, regional jets cannot be profitably operated at $40/seat. The spate of recent airline bankruptcies and mergers is partially fall-out from that fact. Virtually all air travel is less fuel-efficient per passenger than a 4-passenger car would be.

Barring astounding developments in technology or major fuel price drops, regional jets are not the future of commercial air travel. We'd do better figuring out how to get good coverage using a smaller number of superjumbo jets.