[WhiteXFire]

What you're saying is that the belt is moving the wheels as well as the engines. This would be the same idea as what you said...pull the piece of paper from underneath the matchbox car in the opposite direction. That would be the case if the plane was suspended and the wheels were able to respond to the moving belt. BUT, from the perspective of the wheels (here comes that relativity again), the belt IS the ground...it's not moving freely under the wheels. Think of driving down the road, but the road is actually moving as one piece the opposite way. You're moving X mph relative to the road, the road is moving X mph the other way in relation to the earth, and your motion in relation to the earth is zero.