If you spend any time in aviation circles, you will run into the word squawk. A pilot might say "squawking 2200" or you might hear "we have a 7700 out of Denver" on an ATC stream. It sounds like jargon, but the concept is surprisingly simple — and some codes are genuinely dramatic.
What is a squawk code?
A squawk code is a four-digit number that a pilot dials into the aircraft’s transponder. The transponder broadcasts this code to nearby radar, which paints it next to the aircraft on a controller’s screen. Each digit can be 0 through 7, so there are 4,096 possible codes.
The word "squawk" is actually a throwback to World War II radar systems codenamed Parrot — hence squawking. The name stuck.
How squawk codes are assigned
When a flight files a plan, air traffic control assigns it a unique squawk code before departure. The pilot dials it in on the transponder panel, and from that moment the aircraft is digitally tagged on every radar scope in the region. If you ever hear a controller say "squawk 4621," they are giving that aircraft its code for the flight.
Some codes are reserved for special purposes. The most important are the emergency codes, which every pilot in the world knows by heart.
7500 — unlawful interference (hijacking)
Squawk 7500 means the aircraft is being hijacked or otherwise subjected to unlawful interference. A pilot squawking 7500 is silently telling every controller on the network that something is very wrong — without alerting the person in the cabin with them.
This code is rare and triggers an immediate, choreographed response from ATC and law enforcement. You will almost never see it on a flight tracker, and if you do, it is usually a misdial that is corrected within seconds.
7600 — radio failure (lost comms)
Squawk 7600 tells controllers that the aircraft has lost two-way radio contact. The pilot can still fly the plane — they just cannot talk to ATC. Modern aircraft have redundant radios, so this is uncommon, but it does happen.
When a 7600 appears, controllers clear other traffic out of the way and work to establish contact through other means — different frequencies, text messaging via CPDLC, or relaying through a nearby aircraft.
7700 — general emergency
Squawk 7700 is the big one. It means the aircraft has a general emergency — anything serious enough to need priority handling. This could be an engine issue, a medical event on board, a pressurisation problem, smoke in the cockpit, or any number of other scenarios.
On every radar scope in range, a 7700 squawk lights up in red and flashes. The aircraft gets priority routing, airspace is cleared ahead of it, and emergency services are alerted at the destination. Most 7700 events end completely uneventfully — the crew handles the problem, lands safely, and the aircraft is on the ground within minutes.
Other codes worth knowing
- 1200 — the default VFR code in the United States for aircraft flying visually without an ATC clearance
- 7000 — the equivalent default code in most of Europe
- 2000 — a generic "nothing assigned yet" code used in some regions
- 1500–1599 — often reserved for special operations, search and rescue, or military use depending on country
Can you see squawk codes on a flight tracker?
Yes — many flight trackers, including Planes.FYI, show the current squawk code for each aircraft. Most of the time you will see something routine like 2344 or 4106. But every so often a 7700 will pop up, and if you tap into that flight you can usually follow the entire event unfold in near real time. It is one of the quiet fascinations of modern flight tracking: you can watch the world’s airspace respond to an emergency the same moment the controllers do.
Want to see squawk codes live? Open Planes.FYI, tap any aircraft, and look at the flight details panel. You will see its current code next to altitude and speed.
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