Therein lies the entire problem. You're question is made to sound as if the plane's thrust would be countered by the treadmill 'exactly'. So if the jet engine starts up and tries to move one inch forward, the treadmill counters by returning the plane one inch, thus rendering the plane motionless. Now you are sounding as if you're saying the plane is at full thrust from a standstill and the plane never actually 'rolls' the first few feet. You are in essence saying that the planes engine out-thrusts the treadmill in those first few feet, yards, etc.