Could do could do.
We could go around to those airports in advance and park certain planes in certain parking spots, each waypoint (airport) could have instructions to the racer, IE - Land runway 24, taxi to General Aviation Parking 15, note down aircraft that's parked in that space, taxi to runway 09 for takeoff. That way, we would definitely know no ones cheating, as they'd have to land to see the aircraft, but also we're telling them which runway should be used for what, so we don't have someone trying to race to land on 24 and another trying to race to take off on 24.