what about with a space shuttle? it sits stationary until they light those thrusters. good conditions for flight is no wind correct? have you ever stood or walked behind(at a safe distance) a prop plane when they had the engines running? i have. they would sit out there and feather them in front of the hanger to test the systems. when you go to walk out of one hanger to the other, you have to walk right through the air stream. they sit still, but they sure do push alot of air. and with a twin turbo prop for example, the engines are attatched in front of the wings.
so when the props turn, the airstream travels back over the airfoils and could potentionaly create enough lift(not sitting still;rolling) to take off. when you stand 100yds or so behind one with the props turning full speed, you can really feel it. and even more so with a jet engine. what about an f-16 taking off an aircraft carrier? they start off standing still and they dont have that much room to get up. same idea, except the with conveyor/tread mill bullshit.