[96ImpSS]

This is how I understand it: The discrepancy is the difference from the thrust of the engine and the wheels. I guess the problem arises when you have to imagine an enormous treadmill that can move hundreds of mph.

Imagine
The pilot applies thrust to the enigines (say 50%thrust - enough to get the plane to move @200mph not sure of the exact amount just a ballpark guess) the engines spool and the thrust kicks in which moves the wings then the body (collectively several dozen tons) and finally the wheels (supporting the entire weight of the plane) which rotate at 200mph as a result of the thrust applied. THe treadmill then moves 200mph in the opposite direction to compensate. 200mph plane forward - 200 mph treadmill backward=0mph which results in no lift. Without the treadmill the plane moves the 200mmph forwad. Without the thrust the plane moves backwards @ 200mph

Remember the weight of the plane is the connection between the the engines' thrust and the wheels.