The mayday distress signal was first proposed in 1923. Frederick Stanley Mockford, the radio officer at London’s Croydon Airport, devised the spoken emergency word for aviation.
Mockford was asked to find a term that pilots and ground staff could easily understand during a crisis. Because many Croydon flights crossed the English Channel to Paris’s Le Bourget Airport, he adapted the sound of the French phrase m’aider, meaning “help me.” The word was selected for clear recognition in voice communication.
The procedure was introduced for cross-Channel flights in February 1923. It solved a problem that SOS could not fully address: SOS was designed for Morse code, while pilots needed a distinctive spoken signal. In 1927, the International Radiotelegraph Convention formally adopted “mayday” as the radiotelephone distress call, alongside SOS for radiotelegraphy. In an emergency, the word is conventionally repeated three times.