Well, actually, air transport will collapse first, it is doing so right now, as James Howard Kuntsler reports.  But air travel is not a true necessity.  

In the US, agriculture is very oil intensive--it depends on oil derived fertilizers and pesticides, farm labor is mechanized, as is processing--which is extensive--and then the food is transported by truck hundreds or thousands of miles.  Gas prices this spring have doubled--merely doubled--and already the farm sector is experiencing distress.  

Agriculture and transport will collapse about the same time, for the same reason.

I think it will collapse within two years.  

At which point our political system will--umm--no longer function in its usual way . . .

The Fates are kind.