Before the London-bound Air India flight crashed near the Ahmedabad airport on Thursday, June 12, the pilot had reportedly sent out a mayday call to the Air Traffic Control. But as per reports, when the ATC called back, there was no response. The flight, AI171, had carried 242 people on board.
‘Mayday’ is an internationally recognised distress call communicated over radio when there is a life-threatening emergency that requires immediate action. It differs from ‘May Day’, which falls on May 1 and is celebrated as International Labourer’s Day.
The term mayday was first used in 1923 as a way for flights to communicate over radio about mishaps on air. The earlier term used for this was SOS, another internationally recognised distress call for help. This had come into being when the communication was mostly telegraphic and the morse code that was used for SOS was easily understood. SOS was handy for communication from ships.
However, when voices were used to communicate on aeroplanes, there was the risk of misinterpreting the letters of SOS (S taken for F, for instance). Considering the lack of time in such distress situations, an officer was asked to coin a new term. He came up with mayday, as a derivation of the French phrase m’aidez which translates to ‘help me’. The term is usually used thrice: mayday, mayday, mayday, for clarity. Unconfirmed reports suggest that the officer who came up with the term is from Croydon in England, named Frederik Stanley Mockford.
Merriam Webster quotes a Times report of 1923 that made the announcement of changing the distress call to mayday:
Owing to the difficulty of distinguishing the letter "S" by telephone, the international distress signal "S.O.S." will give place to the words "May-day", the phonetic equivalent of "M'aidez", the French for "Help me."
—"New Air Distress Signal," The Times [London], February 2, 1923