Atc Light Signals

Section 91.125 lists the ATC light signals — the visual gun signals that towered airports use when radio communication is unavailable. Every pilot must know these from memory. The signals come in two forms (steady or flashing) and apply differently to aircraft in flight vs aircraft on the ground.

The signals (all colors):

• Steady GREEN — In flight: Cleared to land. On ground: Cleared for takeoff.
• Flashing GREEN — In flight: Return for landing (followed by steady green at proper time). On ground: Cleared to taxi.
• Steady RED — In flight: Give way to other aircraft and continue circling. On ground: STOP.
• Flashing RED — In flight: Airport unsafe — do not land. On ground: Taxi clear of runway in use.
• Flashing WHITE — In flight: Not applicable. On ground: Return to starting point on airport.
• Alternating RED/GREEN — In flight or on ground: General warning — exercise extreme caution.

Acknowledgment from the air (paragraph b): When in flight, the pilot acknowledges receipt of the light signal by rocking the wings during daylight or by flashing the landing or navigation lights between sunset and sunrise.

Acknowledgment from the ground: The pilot acknowledges by moving ailerons or rudder during daylight, or by flashing the landing or navigation lights at night.

Why this still matters in the GPS age: Radio failure is rare but not extinct. Stuck mic, broken pushtotalk button, blown audio panel, electrical failure on the COM bus — any of these put you NORDO into a Class D or busier airspace. Knowing the light signals is the difference between a controlled return and an uncontrolled emergency. The signals are tested on every level of FAA written test.

Reference: AIM 4-2-13 on ATC light signals; FAA-H-8083-25 (PHAK) Chapter 14 on lost-comms procedures.