Squawk code · emergency

Squawk 7600: Lost communications

Squawk 7600 is the transponder code for a radio communications failure (NORDO).

Squawk 7600 means the aircraft cannot talk to air traffic control by radio. It is the standard lost-communications code worldwide. The aircraft itself is usually flying normally; only the voice link is down.

What 7600 means

Pilots and controllers rely on two-way radio for clearances, altitude changes and sequencing. If that link fails, a pilot selects 7600 so that radar displays flag the target with a radio-failure alert (shown as "RDOF" on many US systems). Aviators call this being NORDO, short for "no radio." Causes range from a failed radio or headset to a stuck microphone, an electrical problem, or simply flying out of range of the assigned frequency without getting a handoff.

What pilots and controllers do

US rules (14 CFR 91.185 and AIM 6-4-1) tell an IFR pilot who loses communications exactly what to do, so controllers can predict the flight's path:

• Route: fly the last assigned route, or the route ATC said to expect, or the filed route.
• Altitude: fly the highest of the last assigned altitude, the altitude ATC said to expect, or the minimum IFR altitude for that segment.
• Arrival: begin the approach as close as possible to the expected time.

A VFR pilot who loses radios simply stays in visual conditions and lands as soon as practical. Controllers keep other traffic clear, try other frequencies, ask nearby aircraft to relay, and may use light-gun signals from the tower to clear the aircraft to land.

How 7600 appears on heywhatsflying

We treat 7600 as an emergency squawk and list it on our emergencies now page alongside 7700 and 7500. A 7600 flight on the live map usually looks completely ordinary: steady altitude, normal speed, heading for its destination. Many 7600 events end within minutes when the crew re-establishes contact on another frequency or a backup radio.

How common is it?

Lost-comms events are more common than other emergencies but often short-lived. Across the US you might see one or two 7600 squawks on a given day, most often from general aviation aircraft. Airliners carry two or three independent radios, so a full NORDO situation on an airliner is rare.

Common myths

• "7600 means the plane is in trouble." Not necessarily. It means the radio link is down; the aircraft is usually fine.
• "Fighters will intercept any 7600 aircraft." Interceptions are reserved for aircraft that are unresponsive near sensitive airspace with no explanation. A squawk of 7600 is itself the explanation.

Related codes: 7700 (general emergency), 7500 (unlawful interference) and, for drones, 7400 (lost link). See the full squawk code index.

Questions

What does NORDO mean?

NORDO means "no radio." It describes an aircraft that cannot communicate with air traffic control by voice, which is what squawk 7600 signals.

What does a pilot do after losing radio contact?

An IFR pilot follows set rules: fly the last assigned or expected route and the highest of the assigned, expected or minimum altitude, then begin the approach near the expected time. This lets controllers predict the flight and keep others clear.

Is 7600 an emergency?

It is one of the three special emergency codes and gets special handling, but the aircraft itself is usually flying normally. Many 7600 events end within minutes when contact is restored.