Nick U is absolutely correct. If, as the question states, the conveyor belt maps and matches the speed of the wheels in the opposite direction, then the aircraft will be going nowhere. It will be sitting stationary with the wheels turning. Zero airspeed over the wings = zero lift. An aircraft gets up to takeoff speed by using engine thrust and rolling on the wheels until it has enough airspeed to not require contact with the earth. You'll notice that sometimes when you're flying, a pilot will advance his engines to full power or damn near it before the take-off roll, then sit on the brakes for a while. The aircraft goes nowhere. (I used to do the same when I did engine runs for the aircraft company I worked for) This is exactly the same effect that you have with the conveyor belt working in the opposite direction. It's all about stopping the aircraft accelerating on the wheels and getting sufficient airspeed to generate the lift required for takeoff. Even with aircraft as powerful as fighter jets that cannot be held on the brakes at full power, if the first tiny bit of acceleration (rotation of the wheels) is cancelled out by and then matched by a conveyor belt running in the opposite direction, the aircraft will not move forward, will not accelerate, will remain stationary and will not generate airspeed and lift. Actually, I'd love to see a conveyor belt that could match the wheel speed that a fighter jet on reheat would generate. Or indeed landing gear that could take it!!