What happens when oil dries up?

Hey guys!

Since i am studying energy engineering,i was wondering.Oil resources are finite and are reducing at an increasing rate.Therefore oil prices will get much higher and many airforces will not be able to afford the kerosene in the no so distand future and i think the size of the airforce power will have to decrease everywhere.Also,when oil finally dries up,what will the airplanes be powered then with?Does any airforce think of such a thing,i mean for example F-35 will come to service in several years and i think already,it will be questionable how its sucessor will have to be powered.

It will be a big problem,i think,to find the alternative fuel that would enable military airplanes such performances as they have nowdays.