In the case of a radio failure or a plane not equipped with a radio, air traffic control will use a light gun to direct the airplane. The light gun has a focused bright beam and is capable of emitting three different colors: Red, white and green. These colours may be flashed or steady, and have different meanings to planes in flight or on the ground. Planes acknowledge the instruction by wiggling their wings, or simply moving the ailerons if on the ground.
| | In Flight | On the Ground
|
| Flashing White
| N/A | Return to starting point
|
| Steady Green
| Cleared to land | Cleared for takeoff
|
| Flashing Green
| cleared to approach airport, or return to land | Cleared to taxi
|
| Steady Red
| Continue circling, give way to other aircraft | Stop
|
| Flashing Red
| Airport unsafe, do not land | Immediately taxi clear of runway in use
|
| Alternating Red and Green
| continue current action with caution
|
| Blinking Runway Lights
| vehicles, planes, and pedestrians immediately clear landing area in use
|
