Standard Codes (Memorise!)
These international transponder codes must be known by every pilot by heart. They are safety-critical and set without lookup in emergencies.
Source: ICAO Annex 10 Volume IV; ICAO Doc 4444 PANS-ATM; EU 2017/386.
The four critical codes
7700 — EMERGENCY (Distress)
- Set when: any life-threatening situation.
- Together with: MAYDAY call.
- ATC sees: "EMG" or "DIST" on radar.
- Reaction: highest priority, all other traffic rerouted.
7600 — RADIO FAILURE
- Set when: complete radio failure, after failed restoration.
- ATC sees: "RDO FAIL" or "COM" on radar.
- Reaction: ATC expects standard radio-failure procedure (see lesson "Radio Failure").
7500 — HIJACK (Unlawful Interference)
- Set when: threat on board by third parties.
- Set discreetly if hijacker not aware.
- ATC sees: "HJCK" or "UNLAWFUL" on radar.
- Reaction: security authorities alerted, military interception possible.
2000 — IFR Conspicuity
- Set in IFR without assigned code.
- Crossing an FIR without explicit ATC instruction.
- ATC recognises: IFR flight, but no specific plan assigned.
Other important codes
7000 — VFR Conspicuity (Europe, ICAO standard)
- Set on VFR flights when ATC has not assigned a specific code.
- Standard in EU, Switzerland.
1200 — VFR Conspicuity (USA)
- Set in USA for VFR flights without ATC service.
- Outside USA not standard.
7776 / 7777 — military codes
- Reserved in certain regions — not for civilian use.
Earlier / regional codes
- 0033 (in some EU states): VFR cross-country without ATC.
- 7010 (in some states): local pattern traffic.
→ Consult AIP for regional conventions.
Memorisation
Mnemonic
- 7700 = "Help, help!" (two "7"s)
- 7600 = "Six on Sixty" or "Six O Six" → R for Radio
- 7500 = "Five Hundred Hijack" → associate "five hundred" with "hijack"
Order
Pilot mantra: "7-7 trouble, 7-6 silence, 7-5 hijack".
Practical practice
- Before each flight: walk through 7700/7600/7500 as three-code routine.
- In stress: set without lookup.
- In pre-flight check: practise switching between 1200/7000/assigned.
Cockpit setting
Enter code
4-digit knobs or touchscreen:
- Modern unit: 4 knobs, one per digit.
- Classic unit: knob with "push to set" or toggle.
Mode switch
- STBY: no transmit.
- ON / A: Mode A (code only).
- ALT / C: Mode C (code + altitude).
- S: Mode S.
Confusion risks
Beware:
- 7500 accidentally set → ATC interprets as hijack → military escalation possible.
- 7700 accidentally → emergency response (excessive but quickly cleared via radio).
Best practice: when changing codes, deliberately switch between codes, don't "scroll" through 7500.
Correct change (e.g. from 7000 to 1234):
- Set directly to 1234, not via 7500.
Read-back on code change
ATC: "DEMRA, squawk 4221." Pilot: "Squawk 4221, DEMRA."
Pilot sets code, ATC sees the change on radar.
Cross-reference
- Subject 090 lessons "MAYDAY", "Radio Failure", "Hijack" for application.
- Subject 090 lesson "Modes" for mode theory.