Silly question, huh? So assuming you knew how to fly, and could get past security how much trouble would you have stealing a life flight helicopter or a commuter jet?
Nope, no keys. Easier than stealing a car. BUT before taking off you'd need to file a flight plan and wait for air traffic control to give you go ahead for take off.
Dems the ones with locked doors and keys...Also, you see a lot of... well, not commuter jets, but chartered jets like Gulfstreams, at small airports where no commercial flights go. That'd be the easiest place to steal such a plane.