Mayday is an emergency procedure word used internationally as a distress signal in voice procedure radio communications. It derives from the French venez m'aider, meaning "come help me".[1]
It is used to signal a life-threatening emergency primarily by mariners and aviators but in some countries local organisations such as police forces, firefighters, and transportation organizations may also use the term. The call is always given three times in a row ("Mayday Mayday Mayday") to prevent mistaking it for some similar-sounding phrase under noisy conditions, and to distinguish an actual Mayday call from a message about a Mayday call.
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A mayday situation is one in which a vessel, aircraft, vehicle, or person is in grave and imminent danger and requires immediate assistance. Examples of "grave and imminent danger" in which a mayday call would be appropriate include fire, explosion or sinking.
Mayday calls can be made on any frequency, and when a mayday call is made no other radio traffic is permitted except to assist in the emergency. A mayday call may only be made when life or craft is in imminent danger of death or destruction. Mayday calls are made by radio, such as a ship or aircraft's VHF radio. Although a mayday call will be understood regardless of the radio frequency on which it is broadcast, first-line response organisations, such as coast guard and air traffic control, monitor designated channels: marine MF on 2182 kHz; marine VHF radio channel 16 (156.8 MHz); and airband frequencies of 121.5 MHz and 243.0 MHz. A mayday call is roughly equivalent of a Morse code SOS, or a telephone call to the emergency services. When they receive a mayday call the coast guard may launch lifeboats and helicopters to assist the ship that is in trouble. Other ships that are nearby may divert course to assist the vessel broadcasting the mayday.
Making a hoax mayday call is a criminal act in many countries because of the danger to the rescuers' lives that a search-and-rescue operation can create, the potential for real emergencies elsewhere, as well as the very high costs of such rescue efforts. For example, making a false distress call in the United States is a federal crime carrying sanctions of up to six years imprisonment, and a fine of $250,000.[2] The coast guard can be contacted in situations that are not emergencies (out of fuel, etc.) by calling "Coastguard, Coastguard, Coastguard, this is (name of vessel)", on VHF channel 16. In many countries special training and a licence are required to use a mobile radio transmitter legally, although anyone may legally use one to summon help in a real emergency.
The recommended distress call format includes the word "mayday" spoken three times, followed by the vessel's name or call sign, also spoken three times, then "mayday" and the name or call sign again. Vital information, including the position, nature of the emergency, assistance required and the number of people on board, should follow. A typical message might be:
MAYDAY, MAYDAY, MAYDAY, this is NONSUCH, NONSUCH, NONSUCH. MAYDAY, NONSUCH. Position 54 25 North 016 33 West. My boat is on fire and sinking. I require immediate assistance. Four people on board, are taking a lifeboat. MAYDAY NONSUCH, OVER."
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. A mayday can be sent on behalf of one vessel by another, using a convention called a mayday relay (see below).
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 callsign 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.[3]
Civilian aircraft in the UK and Europe are encouraged to use the following format:
MAYDAY, MAYDAY, MAYDAY; Name of station addressed; Aircraft callsign; Nature of emergency; Intentions of the pilot; Present position (including Altitude or Flight level); Pilot's qualifications; Any other useful information (number of souls on board.)
If unable to establish voice radio communications with air traffic control, aircraft wishing to declare an in-flight emergency should set their radar transponder (squawk) to code 7700.
The Mayday callsign was originated in 1923 by Frederick Stanley Mockford (1897–1962).[4] A senior radio officer at Croydon Airport in London, 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. "Venez m'aider" means "come help me."[5]
Mayday is one of a number of words used internationally as radio code words to signal important information. Senders of urgency calls are entitled to interrupt messages of lower priority. As with Mayday the use of these terms without proper cause could render the user liable to civil and/or criminal charges.
Each of these urgency calls is usually spoken three times; e.g., "Pan-pan, Pan-pan, Pan-pan."
A Mayday relay call is made by one vessel on behalf of a different vessel which is in distress. If a vessel makes a Mayday call and it is not acknowledged by the coastguard after a single repetition and a two-minute wait a vessel receiving the Mayday call should attempt to contact the coastguard on behalf of the Mayday vessel by broadcasting a Mayday relay on their behalf.
A Mayday relay call should use the callsign of the transmitting vessel but give the name and position of the Mayday vessel.
Mayday relay calls can be used to summon help for a vessel which is either too far offshore to contact the coastguard directly or without radio capabilities (though most vessels above a certain size or crew complement are legally required to carry two-way radio equipment, such equipment can potentially be damaged or destroyed).
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.[6] "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.[7][8]
Securite ( /seɪˈkjʊərɨteɪ/;[9] from French sécurité — safety) indicates a message about safety, such as a hazard to navigation or weather information.
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 coastguard (and any other vessels they ask for assistance in handling the emergency). The channel may not be used for normal working traffic until 'seelonce feenee' is broadcast.
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.