Robert M. Gary wrote:
Only if there is an 80 mph tailwind.


If the plane is rolling 80mph against a conveyor going 80mph back the
difference would be zero.


BUT-what is the total friction force from the wheels? Certainly it's
less than the thrust from the engine--I mean, that's what wheels are
designed for, to have as little rolling friction as possible. So let's
add this up... forces acting on airplane are thrust, aerodynamic drag,
and an essentially negligible amount of drag from the wheels. Add it
up, and since the thrust is greater than the drag (as it would be on a
normal takeoff) the airplane accelerates. As I said in another post,
since wheels are designed for minimal friction, just pretend that they
are frictionless, and therefore not even there (anti-gravity airplane).
What is the conveyor belt going to push against now?