Like I said, it is all dependent upon the point of observation. To a guy on the treadmill, the plane is moving forward. To the pilot, the treadmill is moving backward. The question doesn't indicate whether the speed is airspeed or ground speed. If it is airspeed, then air is flowing over the wings, but then the aircraft is hardly moving forward at the same rate the treadmill is moving it backward. If it is ground speed then the plane is not moving forward relative to an observer not on either the treadmill or the plane.