What it means when a plane squawks an emergency
Every aircraft's transponder sends a four-digit "squawk" code that air traffic control assigns. Three of those codes are reserved worldwide as instant emergency signals, and any pilot can dial one in within seconds. When you see a red aircraft on the PlaneTrack map, this is what it is telling you, in plain English.
What is a squawk?
A squawk is a four-digit code (each digit 0-7) set on the aircraft's transponder. Air traffic control uses it to tell one radar blip from another. Most of the time it is a routine number the controller assigns. But three codes are set aside globally as emergencies, and a pilot can select them instantly with a couple of dial turns, even if they cannot say a word on the radio.
Because it is broadcast in the open like any other position message, PlaneTrack can see these codes the moment they change and flag the aircraft for you.
The three emergency squawk codes
Unlawful interference (hijack)
The crew is signalling that the aircraft is being interfered with against their will, most seriously a hijacking. It is the code no one ever wants to see. It is deliberately hard to select by accident.
Radio failure (lost comms)
The aircraft has lost two-way radio contact with air traffic control. The plane is usually flying normally; the crew simply cannot talk to the ground and follows pre-agreed procedures until contact is restored.
General emergency (mayday)
A declared emergency of any kind: a medical problem on board, a mechanical fault, low fuel, a pressurisation issue, and so on. It is the catch-all "we have a serious problem and need priority" signal.
What controllers do about it
An emergency squawk lights the aircraft up on the controller's screen just as it does on ours. Air traffic control gives that flight priority: clearing a path, holding other traffic, offering the nearest suitable airport, and alerting emergency services on the ground to be ready. Most emergencies end safely and routinely; the code simply makes sure everyone gives the flight room and attention.
How PlaneTrack shows them
When an aircraft is squawking one of these codes, PlaneTrack surfaces it in several places, and now labels which of the three it is:
- A red ring around the aircraft on the live map. Click it and the detail panel names the code and its meaning.
- A red banner across the top of the map listing every active emergency, with each code and a short label (Hijack / Lost comms / Emergency).
- The live Emergencies list in the WATCH panel, and the Events feed of noteworthy moments.
- Optional email, browser and iOS push alerts. Turn on an "Any emergency" alert from your notification settings and we will tell you which code it is.
An honest note on coverage. The emergency squawk only reaches us on a fraction of the messages we receive, so emergency detection is best-effort: we surface what we see, but PlaneTrack will not catch every emergency everywhere. A code can also be selected briefly by mistake and cleared again. Treat what you see here as informational, not an official source.
See it live
Open the map to watch traffic in real time, or set up an alert so you know the moment an emergency squawk appears.