Who cares about drag and thrust in this example? For that matter, who cares about wheel bearings, conveyor thickness, and every other variable, again in this example? The fact is, is there is zero air flow over the wings so there is no way it can take off. If we are going to disregard this little fact, then I guess what your saying is is that I can pull a red wagon on the belt and if I pull it fast enough, it eventually it will take off?!?! I am starting to feel like the butt of the joke. Im hoping so becasue it would be scarey to think people actually think the airplane would take off. By the way, if we want to rewrite the riddle and add all the assumptions stated above, then I will gladly agree that the airplane will take off... if there is enough lift involved.