There's the small problem that air travel is environmentally unsustainable, with no fix in sight. It should be heavily taxed to account for the env. externalities.
Taxes to account for environmental externalities (in the case of air travel, noise, CO2, altitude-related pollutants are probably the main things) make sense for everything. Air travel beats road and rail in some cases on this, doesn't in others. Taxes and thus pricing in all the costs would let consumers decide.
