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Originally Posted by Tomkat
This is a silly example.
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No, it's a perfectly fine example.
When you put a toy car against a wall, the force that keeps it to the wall or makes it move up and down alongside it, is your hand. The wheels are merely rotating against the wall as a result of you moving the body of the car, in exactly the same way an airplane's wheels only move as a result of the engines moving the craft across the surface.
Even if you were to put up a toy car against a vertical conveyor belt running downwards, you would still be able to overcome the friction between the wheels and the belt, and move the car upwards, even though the wheels would be spinning like crazy.
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According to your original problem, the conveyor would be moving at the same speed as the wheels of the toy plane.
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No, according to the original problem, the conveyor belt moves at the same speed as the aircraft does; not at the same speed it's wheels are rotating.
Edit: Changed wording of what Mark quoted; obviously the wheels are moving at the same speed as the aircraft since they're attached to it, they're merely rotating at twice the speed that is consistent with the aircraft's velocity.