Learn airport light gun signals for pilots, including ground and airborne meanings, radio-failure actions and acknowledgement procedures.
Airport light gun signals are red, green or white commands aimed from the control tower at an aircraft, chiefly when radio communication has failed. Their meaning changes according to whether the aircraft is airborne or on the ground: for example, steady green means cleared to land in flight but cleared for take-off on the ground.
What does each airport light signal mean?
The standard airport light gun meanings depend on the colour, whether it is steady or flashing, and the aircraft’s position.
| Light signal | Aircraft on the ground | Aircraft in flight |
|---|---|---|
| Steady green | Cleared for take-off | Cleared to land |
| Flashing green | Cleared to taxi | Return for landing; a steady green clearance should follow at the appropriate time |
| Steady red | Stop | Give way to other aircraft and continue circling |
| Flashing red | Taxi clear of the runway or landing area in use | Aerodrome unsafe; do not land |
| Flashing white | Return to the starting point on the aerodrome | Under the ICAO scheme, land at this aerodrome and proceed towards the apron while awaiting the necessary clearances; the US system assigns no airborne meaning |
| Alternating red and green | Exercise extreme caution | Exercise extreme caution |
These are the widely used ICAO-aligned meanings, but national rules can differ. The flashing-white airborne signal is the main variation pilots encounter: it has an ICAO meaning but is marked as not applicable to aircraft in flight in the US light-gun table.
“Return to starting point” does not mean taxi to the runway threshold. It normally means returning to where the aircraft began its movement, such as its parking position or another designated origin.
Why does the same colour have different meanings?
Location changes the meaning because a safe instruction for an airborne aircraft may be inappropriate for one already taxiing.
Green generally permits the next stage of movement, while red restricts it or warns of danger. Pilots must never memorise colour alone: steady versus flashing and ground versus airborne are essential parts of the signal.
A common mistake is interpreting flashing red as a simple stop signal. On the ground, steady red means stop; flashing red means clear the runway or landing area in use.
What should a pilot do after a radio failure?
After a radio failure, the pilot should keep flying or stop taxiing safely, troubleshoot the equipment and watch the control tower for light signals.
- Maintain control and remain predictable. Airborne aircraft should follow the applicable lost-communications procedure and avoid unexpected manoeuvres. On the ground, stop somewhere safe unless movement is necessary to clear a runway.
- Check the radio system. Confirm the frequency, volume, audio-panel selection, microphone or headset connections and push-to-talk switch. Try another installed radio if available.
- Transmit and monitor. Reception may still work even if the tower cannot hear the aircraft. Transmit intentions blind and continue listening for instructions.
- Set the radio-failure transponder code. Select
7600when required by the applicable national procedure, unless ATC has directed otherwise. - Look towards the tower. The controller may aim a narrow, high-intensity signal lamp at the cockpit. If the signal is unclear or may have been intended for another aircraft, do not act on a guess; await a repeat while remaining safe.
An uncontrolled aerodrome, or a controlled airport outside tower operating hours, cannot provide tower light gun signals. The pilot must instead follow the applicable non-towered and radio-failure procedures.
How do pilots acknowledge a light gun signal?
Pilots normally acknowledge by moving the aircraft’s controls or lights so the tower can see that the signal was received.
- In flight during daylight: rock the wings, provided doing so is safe and the aircraft is not on base or final approach.
- In flight at night: flash the landing lights or navigation lights according to the applicable procedure.
- On the ground during daylight: move the ailerons or rudder.
- On the ground at night: flash the landing or navigation lights.
National procedures and aircraft limitations take precedence. A pilot should not make an unsafe control movement merely to acknowledge the tower.
Are light gun signals the same as runway lights?
Light gun signals are directed ATC instructions, whereas runway, taxiway and approach lights are fixed visual aids with meanings that do not change according to the aircraft receiving them.
For the colours and layouts seen around the movement area, our guide to interpreting runway and taxiway lighting covers edge lights, centreline lights, stop bars and runway guard lights. Radio-click systems are different again: pilot-controlled runway lighting procedures switch or adjust airport lights but do not provide an ATC clearance.
A light gun signal also does not provide a detailed taxi route. If communication fails while taxiing, pilots still need the airport diagram and must obey runway signs, markings and holding positions. No green signal removes the need to confirm that it was unmistakably intended for the aircraft and that entering or crossing a runway is authorised.