The conveyor has no conection with the crap that makes a plane go forward, so it would fly ignoring whatever is going on under it. A plane can take off on ice can't it? Or water? And fast too. If the plane (glider) was trying to take off by being dragged real fast by a tow truck, with power to the conveyer, it won't take off.

Wouldn't this be a tough problem instead of a simple one if there was a large fan in front of the plane that blew air at it's wings instead of a conveyer under it's wheels? The plane could get lift but not advance forward.