The Myth - A plane cannot take off while sitting on a conveyor belt moving in the opposite direction.
Verdict - Busted
Notes - The MythBusters first performed a small scale test with a model airplane and a small conveyor belt and were not able to get the model plane to take off from the belt, it merely fell off the front of the conveyor belt. They then tested a model remote-controlled plane on a moving length of paper. The plane moved forward from its starting position and took off. Finally they upgraded to full scale using an actual manned plane and a runway-sized tarp as a makeshift conveyor belt. Like the small scale test, the plane moved forward from its starting position and was able to take off from the conveyor belt. The MythBusters explained that this was possible because unlike cars, an airplane's means of propulsion is through its propeller or jet engine, not its wheels; a car's engine mechanically moves its wheels, which use their contact with the road and the traction it provides to generate forward movement, while the plane's wheels are free-moving and independent of the propeller, which uses air displacement for forward thrust. Therefore, the conveyor belt has no bearing on the forward momentum of the plane.