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.”
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.
While SOS had been used to signal an emergency via morse code, with the increase in air travel it was less practical to use over radio. Frederick Stanley Mockford came up with a new word for signalling an emergency: "mayday".
Mayday got its start as an international distress call in 1923. It was made official in 1948. It was the idea of Frederick Mockford, who was a senior radio officer at Croydon Airport in London. He came up with the idea for “mayday" because it sounded like the French word m'aider, which means “help me."
Pan-Pan-Pan
A serious aircraft system failure, that requires an immediate route or altitude change; Other emergencies that require immediate attention and assistance from the ground.
Wake turbulence poses a major risk to other aircraft, so pilots and ATC use the term “heavy” in radio transmissions as a reminder that the aircraft's wake may be dangerous to others passing behind or below the flightpath of these larger-mass aircraft.
Squawking 7700 in an emergency
The most well know of these is the code 7700. This is used to indicate an emergency of any kind. A pilot will enter this when in an emergency situation - either instructed by ATC after declaring an emergency or without communication if there is no time.
A 'mayday' call indicates an aircraft is in grave and imminent danger and requires immediate assistance.
A pilot who encounters a Distress condition should declare an emergency by beginning the initial communication with the word “Mayday,” preferably repeated three times.
Aviators often speak “pilot English” to avoid miscommunications over radio transmission. “Tree” for instance, means three, “fife” is the number five and “niner” means nine, says Tom Zecha, a manager at AOPA. The variations stemmed from a desire to avoid confusion between similar-sounding numbers, he says.
From military aviation. A pilot reports "no joy" when an attempt to establish visual or radio contact with another aircraft is unsuccessful; or when an attempt to acquire a target - either visually or on tactical radar - is unsuccessful.
"These (PAN and MAYDAY calls) are the emergency notifications that pilots use when there's a problem. There's lots of passengers' lives at stake, so pilots take these calls very seriously, and I think the pilots did a great job."
Supposedly, mayday was coined by Frederick Stanley Mockford, a senior radio officer in Croydon, but we've been unable to substantiate that claim. The call spread well beyond the Channel; the new distress signal's use was reported as far away as Singapore.
SOS is sometimes seen rendered with periods as in S.O.S., but the letters do not represent any actual words and the form approved by the Oxford English Dictionary is SOS. Mayday is a distress call, it is recognized internationally as a message calling for help in a time of extreme distress.
MAYDAY calls are used for life-threatening emergencies. Pan-Pan calls (pronounced "pahn-pahn") are used for urgent situations that are not life-threatening such as your pleasure craft is broken down, out of gas, or lost in fog.
Mayday got its start as an international distress call in 1923. It was made official in 1948. It was the idea of Frederick Mockford, who was a senior radio officer at Croydon Airport in London. He came up with the idea for “mayday" because it sounded like the French word m'aider, which means “help me."
To declare pan-pan correctly, the caller repeats it three times: "Pan-pan, pan-pan, pan-pan," then states the intended recipient, either "all stations, all stations, all stations," or a specific station, e.g. "Victoria Coast Guard Radio, Victoria Coast Guard Radio, Victoria Coast Guard Radio." Then the caller states ...
Panpan calls are messages sent when situations are urgent but do not qualify as distress. The term Panpan derives from the French word Panne which means broken down. An example would be that a vessel has broken down and requires a tow. There is no imminent threat to safety.
Labour Day, also known as Eight Hours Day in Tasmania and May Day in the Northern Territory, commemorates the granting of the eight-hour working day for Australians. It also recognizes workers' contributions towards the nation's economy.
Before the mayday distress call existed, that is before the radio as we know it was in use, telegraph operators used the Morse Code signal — three dots, three dashes, three dots — to communicate distress. The sound of the tapped dots and dashes are often expressed as dih, dih, dih, dah, dah, dah, dih, dih dih.
DISTRESS CALLING. By usage and agreement, there are three levels of distress call: Mayday, Pan Pan and Securité. Each type of call is meant to alert authorities and fellow sailors that a vessel and/or crew are in peril or facing danger. They take precedence, in order, over all other radio traffic.
0000 — A generic code that is not assigned and should not be used. 1200 — VFR aircraft. The default code for all flights–if you aren't asked to set anything else, you should set 1200. 7500 — Hijacking. 7600 — Voice radio failure.
Some squawk codes are reserved, such as 7700 (emergency), 7600 (communication failure), 7500 (hijacking), 1202 (glider), 1200 (VFR), etc. One of these, 7777, is apparently used for "military interception." What does this mean in the United States?