I can't believe this thread is still going This explains it perfectly. If you go on a treadmill and run 5mph forward and the treadmill goes 5mph backwards, you stay still. Why? Because to move forward a person steps on the ground and pushes forward, if the ground is going backwards at the right speed, you don't actually travel anywhere. However, the mistake people are making is applying this to a plane and assuming it's correct. THINK about how a plane moves forward on a runway. Does the engine turn a shaft that turns the wheels to provide thrust like in a car? No, it doesn't. The wheels are not there to provide thrust for the plane, to make the plane go forward, simplifying it a bit; the propeller (or jet engine) pushes air backwards, which in turn pushes the plane forwards. Just like swimming. The wheels are just free to move, they have very little effect on the planes movement. So long as the planes forward thrust has overcome the initial friction of the bearing, the treadmill can be going a bazillion mph and it wouldn't effect the planes movement. The wheels would be going really, really fast, but the plane doesn't care because the forward thrust isn't in any way related to the wheels.