Transponder Squawk Codes
Avionics & Flight Operations · 7 specs
Direct Answer
Air traffic control secondary surveillance radar (SSR) interrogates airborne transponders to receive 4-digit octal Squawk Codes (digits 0–7), with internationally reserved codes for emergency conditions: 7500 (Hijacking), 7600 (Radio Failure), and 7700 (General Emergency).
Specs
| Standard Authority | ICAO Annex 10 / FAA Order JO 7110.65 |
| Digit Base | 4-digit Octal (0000 to 7777, providing 4,096 distinct discrete codes) |
| Emergency Hijack Code | 7500 (Unlawful Interference) |
| Emergency Comms Failure | 7600 (Lost Radio Communications) |
| General Emergency Code | 7700 (Mayday / Immediate In-flight Emergency) |
| VFR Standard (US/Canada) | 1200 |
| VFR Standard (Europe/ICAO) | 7000 |
International Emergency Squawk Code Rules
When an emergency code is squawked, it triggers an immediate flashing red beacon and audible alarm on all ATC radar consoles:
- Code 7500 (Hijack): "Seven-five, man with a knife / taken alive." Controller will silently monitor without verbal challenge to protect crew safety.
- Code 7600 (Radio Failure): "Seven-six, radio needs a fix / in a fix." Pilot executes lost comms procedures (fly assigned route, squawk 7600, watch for light gun signals).
- Code 7700 (General Emergency): "Seven-seven, going to heaven / falling from heaven." Automatically grants absolute priority over all other airspace traffic.