It is used to signal a life-threatening emergency primarily by aviators and mariners, but in some countries local organizations such as firefighters, police forces, and transportation organizations also use the term. The call is always given three times in a row ("Mayday Mayday Mayday") to prevent its being mistaken for some similar-sounding phrase under noisy conditions, and to distinguish an actual Mayday call from a message about a Mayday call.
The Mayday procedure word was originated in 1923, by a senior radio officer at Croydon Airport in London. The officer, Frederick Stanley Mockford, was asked to think of a word that would indicate distress and would easily be understood by all pilots and ground staff in an emergency. Since much of the traffic at the time was between Croydon and Le Bourget Airport in Paris, he proposed the word "Mayday" from the French "m'aider", a shortened version of "venez m'aider" (meaning "come and help me").
Before the voice call "Mayday", SOS was the Morse code equivalent of the Mayday call. In 1927, the International Radiotelegraph Convention of Washington adopted the voice call Mayday as the radiotelephone distress call in place of the SOS radiotelegraph (Morse code) call.
If a Mayday call cannot be sent because a radio is not available, a variety of other distress signals and calls for help can be used. Additionally, a Mayday call can be sent on behalf of one vessel by another, using a convention called a Mayday relay.
Civilian aircraft making a Mayday call in United States airspace are encouraged to use the following format (omitting any portions as necessary for expediency or where they are irrelevant):
Mayday, Mayday, Mayday; (Name of station addressed); Aircraft call sign and type; Nature of emergency; Weather; Pilot's intentions and/or requests; Present position and heading, or if lost then last known position and heading and time when aircraft was at that position; Altitude or Flight level; Fuel remaining in minutes; Number of souls on board; Any other useful information.
Other urgent calls
Pan-pan (from the French: panne—a breakdown) indicates an urgent situation of a lower order than a "grave and imminent threat requiring immediate assistance", such as a mechanical breakdown or a medical problem. The suffix medico used to be added by vessels in UK waters to indicate a medical problem (Pan-pan medico, repeated three times), or by aircraft declaring a non-life-threatening medical emergency of a passenger in flight, or those operating as protected medical transport in accordance with the Geneva Conventions. "Pan-pan medico" is no longer in official use.
Sometimes the phrase "declaring emergency" is used in aviation. This is the same as calling "Mayday". For example, Swissair Flight 111 radioed "Swissair one eleven heavy is declaring emergency" on discovering their situation.
However, ICAO recommends the use of the standard "Pan-pan" and "Mayday" calls instead of "declaring an emergency". Cases of pilots using phrases other than "Pan-pan" and "Mayday" have caused confusion and errors in aircraft handling.
The following calls may be made only by the vessel in distress or the responding authority:
Seelonce Mayday or Seelonce Distress means that the channel may only be used by the vessel in distress and the Coast Guard (and any other vessels they ask to assist in handling the emergency). The channel may not be used for normal working traffic until "seelonce feenee" is broadcast.
"SEELONCE MAYDAY" (followed by the name of the disturbing station) may only be sent from the vessel in distress. "SEELONCE DESTRESSE" (followed by the name of the disturbing station) may only be sent from a station which is not participating on the emergency traffic.
The expressions Stop Transmitting—Distress and Stop Transmitting—Mayday are the aeronautical equivalents of Seelonce Mayday.
Seelonce Feenee (French: silence fini—silence finished) means that the emergency situation has been concluded and the channel may now be used normally. The word prudonce (prudence—"caution") can also be used to allow restricted working to resume on that channel.
Distress Traffic Ended is the aeronautical equivalent of seelonce feenee.
- Aircraft emergency frequency
- Call for help
- Distress signal
- Global Maritime Distress Safety System
- Vessel emergency codes
- "Why Mayday?". Research Questions. National Maritime Museum Cornwall. Retrieved 1 May 2013.
- Oxford Dictionaries, "Mayday"
- In 1927, the International Radiotelegraph Convention of Washington adopted the word "Mayday" as radiotelephone distress call Radiotelegraph Convention of Washington, page 81.
- Aeronautical Information Manual, paragraph 6-3-2, "Obtaining Emergency Assistance", Federal Aviation Administration, 1999
- No Joke
- ICAO Annex 10 V2 Section 5.3
- Swissair Flight 111 Transcript
- NTSB accident investigation report for Pinnacle Airlines Flight 3701
- "ICAO Standard Phraseology" (PDF). SKYbrary. Retrieved 13 June 2013.
- "Aircraft Fuel Status and Communication Procedures" (PDF). Hong Kong Civil Aviation Department. Retrieved 13 June 2013.