An air traffic controller using a light gun that can be used to control aircraft with radio failure.

In the case of a radio failure or aircraft not equipped with a radio, or in the case of a deaf pilot, air traffic control may use a signal lamp (known colloquially as a light gun) to direct the aircraft. The signal lamp has a focused bright beam and is capable of emitting three different colours: red, white and green. These colors may be flashed or steady, and have different meanings to aircraft in flight or on the ground. Planes can acknowledge the instruction by rocking their wings, moving the ailerons if on the ground, or by flashing their landing or navigation lights during hours of darkness.

Signal Aircraft in flight Aircraft on the ground Ground vehicles or personnel Flashing white ICAO – Land at this airport and proceed to apron (this is not a clearance to either land or taxi. Clearances to land and taxi will follow.)

FAA – Not applicable Return to starting point Return to starting point Steady green Cleared to land Cleared for takeoff Cleared to cross/proceed Flashing green Cleared to approach airport, or return to land Cleared to taxi N/A Steady red Continue circling, give way to other aircraft Stop Stop Flashing red Airport unsafe, do not land Immediately taxi clear of runway in use Clear the taxiway/runway Alternating red and green Exercise extreme caution Exercise extreme caution Exercise extreme caution Blinking runway aviation lights Vehicles, planes, and pedestrians immediately clear landing area in use