Quote Originally Posted by Ruiner
No, the treadmill is motorized, but the wheels of the plane are free spinning. The treadmill has torque, but it ONLY applies it to wheels that are free spinning.

Your dyno question was wrong in a sense. The wheels on the car would need to be free spinning (in neutral) as well. Will the dyno work and apply torque to the car if the car is in neutral? Nope. Just like the treadmill will not apply torque to the plane if the wheels are free spinning.
Oh okay,

but I was NOT talking in the sense that your car is in neutral + jet engine, no, not that.

I was talking about the plane's wheels = the same as the dyno's rollers.
And the treadmill = the car itself.

Lift up or not is based on air pressure. if there aren't any, plane will not lift off. Also, the treadmill will adjusting its negative velocity accordingly to the plane's.

Using the car vs dyno was a bad example. It was only to show you that the treadmill does output torque and HP in negative X direction to cancel out the free rolling velocity in positive X direction.