Begs the question: What % of air travel is essential?
I would argue that medivac, medical clinic, fire-fighting, SAR, some survey ops, some maritime patrol, things along that line are..... but what about all those airliners....?
If you didn't have a vested interest (like me!) in it continuing to grow forever, what amount of those bums in those seats really need to be there? Tourism? "Business" trips? Military Transports to fly politicians around?... The Roulettes? Exporting live Crayfish? Importing Beef TO Australia? Transporting F1 Racecars or Racehorses from Dubai?
Put it this way - if oil gets to $150+ a barrell quickly, I guess the market may well determine it all for us.
How will the taxpayer then feel about a Government 737 flying John Howard, his advisors, and the Australian Press to Washington to get a farewell photo opportunity with ..... the guy who helped a great deal in getting the oil price so high!?
Perhaps the pure economics of flying may solve the environmental problem.