Free-spinning wheels, not connected to drivetrain. Essentially, the fuselage is suspended in air and then moved upon thrust of the engines. So the plane will move forward, the conveyor matching speed, however the wheels will spin backwards.
this explains a lot more than your picture
h:
The wheels will spin the same way they normally do, just twice as fast.
Now here's a scenario: the conveyor belt is going in the same direction of the plane, maintaining the same speed. The plane accelerates and the conveyor belt follows suit. The plane gets up to take-off speed and leaves the ground with the wheels never turning :eek5:
h: