Mayday is an emergency procedure word used internationally as a

distress signal A distress signal, also known as a distress call, is an internationally recognized means for obtaining help. Distress signals are communicated by transmitting radio signals, displaying a visually observable item or illumination, or making a soun ...

in voice-procedure radio communications. It is used to signal a life-threatening emergency primarily by aviators and mariners, but in some countries local organizations such as firefighters,

police The police are a constituted body of persons empowered by a state, with the aim to enforce the law, to ensure the safety, health and possessions of citizens, and to prevent crime and civil disorder. Their lawful powers include arrest and th ...

forces, and transportation organizations also use the term. Convention requires the word be repeated three times in a row during the initial emergency declaration ("Mayday mayday mayday") to prevent it being mistaken for some similar-sounding phrase under noisy conditions, and to distinguish an ''actual'' mayday call from a message ''about'' a mayday call.

History

The "mayday" procedure word was conceived as a distress call in the early 1920s by Frederick Stanley Mockford, officer-in-charge of radio at Croydon Airport, England. He had been 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 air traffic at the time was between Croydon and Le Bourget Airport in Paris, he proposed the term "mayday", the phonetic equivalent of the French ("help me") or (a short form of , "come ndhelp me"). The term is unrelated to the holiday

May Day May Day is a European festival of ancient origins marking the beginning of summer, usually celebrated on 1 May, around halfway between the spring equinox and summer solstice. Festivities may also be held the night before, known as May Eve. Tr ...

. Following tests, the new procedure word was introduced for cross-Channel flights in February 1923. The previous distress call had been the Morse code signal SOS, but this was not considered suitable for voice communication, " ing to the difficulty of distinguishing the letter 'S' by telephone". In 1927, the International Radiotelegraph Convention of

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

adopted the voice call "mayday" as the radiotelephone distress call in addition to the SOS radiotelegraph (Morse code) signal.

Mayday calls

If a mayday call cannot be sent because a radio is not available, a variety of other

s and calls for help can be used. Additionally, a mayday call can be sent on behalf of one vessel by another; this is known as a mayday relay. Civilian aircraft making a mayday call in United States airspace are encouraged by the

Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic ...

to use the following format, omitting any portions as necessary for expediency or where they are irrelevant (capitalization as in the original source): Making a false distress call is a criminal offence in many countries, punishable by a fine, restitution, and possible imprisonment.

Other urgent calls

Pan-pan

Pan-pan The radiotelephony message PAN-PAN is the international standard urgency signal that someone aboard a boat, ship, aircraft, or other vehicle uses to declare that they have a situation that is urgent, but for the time being, does not pose an immed ...

" (from the French: ', 'a breakdown') indicates an urgent situation, such as a mechanical failure or a medical problem, of a lower order than a "grave and imminent threat requiring immediate assistance". The suffix "medico" originally was to be added by vessels in British 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 upright=1.15, Original document in single pages, 1864 The Geneva Conventions are four treaties, and three additional protocols, that establish international legal standards for humanitarian treatment in war. The singular term ''Geneva Conve ...

. "Pan-pan medico" is no longer in official use.

Declaring emergency

Sometimes the phrase "declaring emergency" is used in aviation, as an alternative to calling "mayday". For example, in 1998 Swissair Flight 111 radioed "Swissair one-eleven

heavy Heavy may refer to: Measures * Heavy (aeronautics), a term used by pilots and air traffic controllers to refer to aircraft capable of 300,000 lbs or more takeoff weight * Heavy, a characterization of objects with substantial weight * Heavy, ...

is declaring emergency" after their situation had worsened, upgrading from the "pan-pan" which was declared earlier. However, the

International Civil Aviation Organization The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international a ...

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.

Silencing other communications traffic

"Seelonce mayday" (using an approximation of the French pronunciation of ') is a demand that the channel only be used by the vessel/s and authorities involved with the distress. The channel may not be used for normal working traffic until "seelonce feenee" is broadcast. "Seelonce mayday" and "seelonce feenee" may only be sent by the controlling station in charge of the distress. The expression "stop transmitting – mayday" is an aeronautical equivalent of "seelonce mayday". "Seelonce distress" and "prudonce" are no longer in use since ITU WRC-07. The format for a "seelonce mayday" is MAYDAY, All Stations x3 or nterfering stationx3, this is ontrolling station SEELONCE MAYDAY. ITU RR 2016. "Seelonce feenee" (from French ', 'silence finished') means that the emergency situation has been concluded and the channel may now be used normally. "Distress traffic ended" is the aeronautical equivalent of "seelonce feenee". The format for the "seelonce feenee" is MAYDAY, All stations x3, this is ontrolling stationx3, date and time in UTC, distressed vessels MMSI number, distressed vessels name, distressed vessels call sign, SEELONCE FEENEE. ITU RR 2016.

References

External links

Handling Distress and Help Calls

ACP135(F): Communications Instructions: Distress and Rescue Procedures

*
Transport Canada: Radio Distress Procedures Card TP9878
{{DEFAULTSORT:Mayday (Distress Signal) Emergency communication History of air traffic control International telecommunications Rescue Distress signals Telecommunications-related introductions in 1923