I think that the amount of oil supplies available in the world is something like 50-75 years. However, air travel is rapidly expanding in the Developing world, and we are seeing an explosion of cars in China. Anyone think that air travel's economics could be threatened any time soon by oil shortages?
I believe we are less than 2 decades from exhausting non-Middle Eastern oil supplies. While 50 years seems like a ways off, I could imagine problems that could bring pain early to the air industry.
I guess greater fuel economy for cars as well as alternative fuels and hybrid cars, could help save oil for jet fuel.
On an optimistic note, I could see successful oil conservation efforts pushing the global oil supply out for 100 years or more.