Quote Originally Posted by Krupski View Post
The jet moves forward due to the thrust of the engines. The forward motion also causes the landing gear wheels to rotate. If the "treadmill" moved as fast as the jet, the effect would be that the wheels would be stationary, but the airplane would still take off and fly...
How does a plane fly? It flies when the air movement is sufficient to provide lift. If the airplane is in the same spot relative to the ground it cannot provide lift. The treadmill is always canceling out any thrust/wheels turning except keeping up with the treadmill.