boogie-nicey: I strongly disagree that the inevitable result of an aviation fuel tax would be "no progress on the environmental responsibilities". Money talks. Airlines are updating their fleets because the price of oil is rising, and if the price of fuel were further increased by taxation, you can be sure Boeing and the rest would pump huge resources into developing fuel efficient and "zero emission" alternatives. The fuel cell for example, specifically the hydrogen cell, consumes hydrogen and oxygen to produce electricity, in the process emitting water vapour. Water vapour is also problematic when dumped in the upper troposphere, but less so than CO2. Airlines could be given incentives to fly at low altitudes, using planes with a very high wing loading to minimise the effects of turbulence. On the ground, the hydrogen and oxygen needed for fuel cells would be extracted from water with electricity, which should be supplied by "green" power sources.
This is all technologically achievable on a small scale today, but it's far too expensive to implement commercially. This is why I favour smart legislation encouraging technological development. When George Bush says we can rely on technology to save us he is probably right: he just fails to appreciate that the free market will not produce this technology within several decades without careful regulation. The reason that American cars are so inefficient compared to European and Japanese models boils down to fuel taxation differences.