'Mayday' is an internationally recognized distress signal. 'May Day' is a spring holiday and, in some places, a celebration of working people. The terms sound similar, but they have different origins. They are not spelled the same way. Mayday is an internationally recognized radio word to signal distress.

The term 'Mayday' originates from the French phrase 'm'aider' which means 'help me'. It was first adopted as a distress signal for aviation in the early 1920s. The credit for its implementation goes to Frederick Stanley Mockford, a senior radio officer at London's Croydon Airport.

Due to radio interference and loud ambient noise, pilots are told to repeat the word three times: "Mayday, mayday, mayday." The repetition also serves to help radio operators distinguish the transmission from others that simply refer to the mayday call.

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.”