Squawk Codes
A squawk code is a four-digit code (0000–7777, octal) that an aircraft transmits via its transponder. Air traffic control assigns each flight a unique code to identify aircraft on radar. Besides unique codes, a number of reserved codes have a fixed meaning.
⚠ Emergencies
7700
General emergency Mayday
The pilot has declared an emergency. This can be due to technical problems, a medical emergency on board, low fuel, or other life-threatening situations. The aircraft immediately receives priority from air traffic control.
7600
Radio failure NORDO
The aircraft cannot establish radio contact with air traffic control (NORDO = No Radio). The pilot squawks 7600 so the radar controller knows communication isn't possible. Fixed procedures exist for how the aircraft continues its flight in this case.
7500
Hijack Hijack
The aircraft is being hijacked or there is unlawful interference on board. This is the most serious signal in aviation. Authorities are alerted immediately and the aircraft is tracked closely.
✈ Standard VFR and IFR Codes
7000
VFR flight VFR
Standard squawk for Visual Flight Rules flights in European airspace without an ATC-assigned code. Many light aircraft and gliders use this code.
2000
Entering controlled airspace IFR
An aircraft entering controlled airspace before ATC has assigned a code. Once air traffic control makes contact, a unique code is issued.
1000
IFR without assigned code IFR
Used in European airspace for IFR flights (Instrument Flight Rules) that have not yet received an individual squawk from air traffic control. In practice, rarely visible for long.
1200
VFR flight, North America VFR
The North American equivalent of 7000: standard VFR squawk in the US and Canada. Sometimes visible over the Atlantic on flights departing from the US.
0000
Not assigned
The default value on transponder startup, or when no code has been entered yet. An aircraft squawking 0000 has likely just powered on its transponder or is in the process of changing codes.
✈ Military Codes
7001
Military high-speed flight Military
Used by military jets flying supersonic or at high speed. Commonly seen from fighter jets operated by air forces during training flights.
7004
Military aerobatics Military
Training flights and aerobatic demonstrations by military aircraft. Visible at airshows and exercises.
7777
Military interception Military
A military aircraft is actively intercepting another aircraft. Very rare under normal circumstances.
🔍 Other Special Codes
7003
Head of state flight Military
Reserved for flights carrying heads of state (such as Air Force One in the US). Reserved for similar state flights elsewhere too.
0021
Search and Rescue
Used by SAR flights during search-and-rescue operations at sea or on land. Commonly seen from coast guard helicopters and rescue flights over coastal waters.
🔄 Individually Assigned Codes
0001–7777
ATC-assigned code
By far most squawk codes you'll see — like 5356, 3421 or 2714 — are individually assigned by air traffic control. They have no fixed meaning: ATC gives each flight a unique code at the start so the aircraft can be distinguished on radar from every other flight in the same airspace.
The code is temporary: once a flight leaves the airspace or radar contact ends, the code is released and can be reused for another flight. Each region/ACC (Area Control Centre) has its own block of codes assigned — but this isn't visible from the code itself.
What you can infer:
• Code is not 7700/7600/7500 → no emergency
• Code is not 7000/2000/1200 → flight has active radar contact with ATC
• Code changes during the flight → aircraft has been handed off to another sector or ACC
The code is temporary: once a flight leaves the airspace or radar contact ends, the code is released and can be reused for another flight. Each region/ACC (Area Control Centre) has its own block of codes assigned — but this isn't visible from the code itself.
What you can infer:
• Code is not 7700/7600/7500 → no emergency
• Code is not 7000/2000/1200 → flight has active radar contact with ATC
• Code changes during the flight → aircraft has been handed off to another sector or ACC
🔔 How to Read a Squawk Code
Squawk codes are octal numbers: the digits range from 0 to 7 (no 8 or 9). This gives 4,096 possible codes (8⁴). Most are temporarily assigned by ATC — only the codes above in the colored blocks have a fixed reserved meaning.
The three emergency codes (7500, 7600, 7700) are highlighted in red on the map and in the table. Clicking a squawk code in the popup takes you to the matching explanation on this page — a regular ATC code takes you to the section above.