All travel, and especially long-haul air travel, has adverse ecological consequences. Unlike trains, which if electrified can get power from a variety of renewable sources, airplanes all fly on fossil fuel ("jet fuel" is kerosene). The present window of opportunity for transoceanic air travel -- affordable to large numbers of people -- is likely to be, in historical terms, a brief one before the world runs out of oil. There is no such thing as "sustainable" or "low-impact" air travel.