MAYDAY

What is a MAYDAY call

MAYDAY is the word that signals an emergency situation that directly threatens the safety of the aircraft or its occupants and requires immediate assistance. It's repeated three times in a row at the start of the message: "MAYDAY MAYDAY MAYDAY".

The word's origin is French: it comes from "m'aider" (help me), chosen in the 1920s as a vocal emergency signal that was: - Pronounceable uniformly across all languages - Unmistakable for any other word - Universal for radio and telephony

When you say MAYDAY

The ICAO criterion is clear: grave and immediate danger to flight safety. Typical examples:

• Engine failure or complete engine quit
• Fire on board (engine, cabin, baggage)
• Loss of structural control (control failure, structural damage)
• Decompression or serious medical issues on board
• Critical fuel (insufficient to reach a suitable airfield)
• Suddenly severe weather putting the aircraft at risk
• Total disorientation in IMC for a VFR pilot

The controller's practical rule: "if you're in doubt whether it's MAYDAY or not, it IS MAYDAY." It's always better to declare emergency and downgrade later than to stay silent until it's too late.

Standard structure of a MAYDAY message

A complete MAYDAY message follows this template:

1. MAYDAY MAYDAY MAYDAY — the emergency call
2. Whom you're calling — station name (if known), or "all stations"
3. Aircraft identification — full callsign
4. Nature of the emergency — what's happening
5. Pilot's intentions — what you're doing or want to do
6. Position, altitude, speed — where you are in three dimensions
7. Persons on board (POB) — how many you are
8. Fuel remaining — how much flight time left
9. Other useful info — anything the controller needs to know

Squawk code 7700

When you declare MAYDAY, you should simultaneously set the transponder to 7700 (if you have one operational). This code is the general emergency signal and is visible on all area ATC radars as a flashing alarm.

Even if the radio doesn't work, the 7700 alone is sufficient to activate the ATC emergency procedure. See Squawk Codes.

What the controller does on hearing MAYDAY

On the tower/center side, a MAYDAY call triggers a standardized sequence in seconds:

1. Silences the frequency to other non-urgent flights (with the phraseology "All stations, stop transmitting, MAYDAY").
2. Devotes total attention to the emergency aircraft.
3. Alerts the D-supervisor (shift supervisor) of their unit.
4. Activates rescue services (fire, helicopter rescue, ambulances) via direct line.
5. Coordinates with adjacent FIRs if the aircraft moves into another jurisdiction.
6. Continues talking with the pilot providing weather, vectors, alternate frequencies.

All this without unnecessary questions. The controller will only ask the essential questions to coordinate rescue.

Cancelling a MAYDAY

If the situation resolves itself (engine restarts, fire extinguished, medical symptom passes), the pilot can cancel the MAYDAY:

"Lugano Tower, HB-PMR, cancel MAYDAY, situation resolved, request normal proceeding to Locarno."

The controller confirms with "MAYDAY cancelled" and frees the frequency to normal traffic. The emergency report is still archived by the authority — it's not a "non-emergency", it's an emergency that resolved.

Swiss specifics

Summary — to remember

1. MAYDAY = grave and immediate emergency. When in doubt, say it.
2. Three times at the start. "MAYDAY MAYDAY MAYDAY".
3. Squawk 7700 simultaneously.
4. Message structure: identification, nature, intentions, position/altitude, POB, fuel.
5. No penalty for a MAYDAY in good faith. Severe penalty for not declaring it.
6. 121.500 MHz = international emergency frequency, always on standby.

Sources

• ICAO Annex 10 — Aeronautical Telecommunications, Volume II, Chapter 5
• ICAO Doc 9432 — Manual of Radiotelephony, Chapter 8
• AIP Switzerland — GEN 3.6 (Search and Rescue services)
• REGA — Schweizerische Rettungsflugwacht, procedures