Aviation light signal reference
If an aircraft loses radio contact, the control tower can still direct it using a steerable light gun that emits steady or flashing beams of green, red or white light. Each signal carries a defined meaning, but that meaning changes depending on whether the receiver is an aircraft in flight, an aircraft on the ground, or a vehicle on the movement area. This tool lets you pick the context and shows the meaning of every signal for that situation.
How it works
The control tower selects a colour and a pattern (steady or flashing). The same colour can mean opposite things by context: a steady green clears an airborne aircraft to land but clears a ground aircraft for takeoff, while a flashing red tells an airborne pilot the airport is unsafe but tells a ground aircraft to taxi clear of the active runway. Some signals are only used in certain contexts — flashing white is a ground/vehicle signal (“return to your starting point”) and is not used in flight. Alternating red and green always means “exercise extreme caution”.
Complete signal table
| Signal | Aircraft in flight | Aircraft on ground | Vehicles / pedestrians |
|---|---|---|---|
| Steady green | Cleared to land | Cleared for takeoff | Cleared to cross/proceed |
| Flashing green | Return for landing | Cleared to taxi | Not applicable |
| Steady red | Give way; continue circling | Stop | Stop |
| Flashing red | Airport unsafe; do not land | Taxi clear of runway in use | Clear runway/taxiway |
| Flashing white | Not used | Return to starting point | Return to starting point |
| Alternating red/green | Exercise extreme caution | Exercise extreme caution | Exercise extreme caution |
Why context changes the meaning
The light gun system was designed around the operational reality that an airborne aircraft and a ground aircraft need opposite instructions for the same situation. “Go ahead” for an aircraft already on approach means “land” — but for an aircraft sitting at the holding point it means “take off.” Using separate colour-pattern combinations for each outcome, rather than different colours for each context, minimises the number of codes a pilot must memorise while keeping all six outputs visually distinct.
The flashing-versus-steady distinction within a colour conveys urgency: a steady red is an instruction to stop or give way, while a flashing red is an immediate safety directive (leave the runway now; do not land). Understanding this structure lets you reason about unfamiliar signals rather than just rote-memorise the table.
Acknowledging a light signal
Pilots acknowledge a received signal differently depending on phase of flight:
- In flight, daytime: rock the wings to indicate the signal was received and understood.
- In flight, night: flash the landing lights or navigation lights.
- On the ground, daytime: move the ailerons and rudder to show acknowledgement.
- On the ground, night: flash the landing lights.
The tower watches for this acknowledgement before assuming the instruction was received.
Regulatory framework
The signals are standardised in FAA AIM Chapter 4-3-13 and ICAO Annex 2, which is why commercial and general aviation pilots everywhere learn the same chart. The FAA and ICAO tables are functionally identical for these six signal types. This page is a study reference — in an actual NORDO (no-radio) situation, follow your current AFM lost-comms checklist and the applicable regulatory guidance.