I've done a FPV flight with my quadcopter, controlling it from a car, during 2,5km. It was a great experience! At 3:45 the quad reached more than 60km/h (~40mph)
WARNING: this video was done after testing the quadcopter structure, crash resistance, vibration, aerodynamics, propellers resistance, wires connections, radio range in the worst conditions, radio failsafe, altitude hold and return to home testing, tuning of PID flight controllers, battery redundancy, calculating the flight time and many other tests, besides attaching a parachute system to the quadcopter and performing the flight with little traffic. In the worst case, the quadcopter would land using the parachute.