MAYDAY in Morse Code
The spoken distress call, written in Morse — and the important reason the two are not interchangeable.
MAYDAY in Morse code
Character by character
| Character | Morse code | Play | Copy |
|---|---|---|---|
| M | -- | ||
| A | .- | ||
| Y | -.-- | ||
| D | -.. | ||
| A | .- | ||
| Y | -.-- |
Mayday is spoken, SOS is sent
This is the distinction worth getting right. Mayday is a voice procedure word, used on radiotelephony and spoken three times: "Mayday, Mayday, Mayday". SOS is the Morse signal, sent as one unbroken run of nine elements. They mean the same thing — grave and imminent danger, immediate assistance required — but they belong to different modes.
Historically they arrived from opposite directions. SOS was agreed in 1906, when radio meant Morse. Mayday came in 1923, when voice radio had become practical and aviation needed something that carried clearly over a noisy channel in both English and French.
So if you are actually signalling in Morse, send SOS. Spelling out M-A-Y-D-A-Y in Morse is a translation exercise, not a distress procedure, and an operator hearing it would read it as ordinary text rather than as a call for help.
Where the word comes from
It has nothing to do with the month. Frederick Stanley Mockford, a radio officer at Croydon Airport in London, was asked in 1923 to devise a distress word that would be understood by both British and French crews on the busy route to Le Bourget.
He proposed "mayday", an anglicised spelling of the French m'aider — help me, shortened from venez m'aider, come and help me. It was chosen for how it sounds: two clear syllables that survive a bad radio link and cannot be confused with anything else in routine traffic.
The triple repetition is part of the procedure, not emphasis. Saying it three times distinguishes a genuine call from someone merely mentioning the word — the same reasoning that made SOS a single unbroken sequence rather than three separate letters.
Frequently Asked Questions
What is MAYDAY in Morse code?
MAYDAY is -- .- -.-- -.. .- -.--. In a real emergency on Morse you would send SOS instead, since Mayday is a voice procedure.
Is Mayday or SOS correct for Morse?
SOS. Mayday is spoken over voice radio; SOS is the Morse signal. Both mean a life-threatening emergency needing immediate help.
Why is it called Mayday?
It comes from the French m'aider, meaning help me. It was chosen in 1923 by a radio officer at Croydon Airport because it was clear to both English and French speakers over a poor radio link.