The phrase, “Mayday”, is a callsign used by vessels, aircraft, or any such carrier of people that is transmitted by a person when they are in grave and imminent danger. It is a sign to all listens of the Mayday call that immediate assistance is required for the transmitters safety or that that it is to late for such assistance. It originated in 1923 by a senior radio officer at Croydon Airport in London, called Frederick Stanley Mockford. He was asked to think of a distress call that could be easily understood by all pilots and ground personal in the event of an emergency. The word “Mayday” was chosen from the French word “m’aide,” meaning, “come help me” because of the high level of air traffic between London and France at the time. The one advantage of a Mayday call over all other distress calls is that when being transmitted over a frequency no other radio traffic is permitted unless it is directed to the distressed vessel in order to help.
Though the Mayday distress signal can be transmitted over any frequency aircraft have special frequencies that are specifically for distress calls. The frequency 121.5 MHz and 243 MHz are left unused by air traffic for the purposed of distress calls and are constantly monitored by air traffic control. A pilots ELT, or emergency locater transmitter, also broadcast over those frequencies in an event it is activated. The Mayday call is the verbal equivalent of an SOS.
When air traffic control receives a Mayday transmission they must launch search and rescue operations in search of the aircraft sending it. Any aircraft in the area are asked to keep their eyes pealed for any activity in order to assisted search and rescue. In the United States as well as many other countries it is a criminal act to broadcast a Mayday distress signal when not actually in danger. The cost of running a search and rescue operation is extremely costly and puts many peoples lives at risk allowing for the bending of Federal Aviation Regulations in order to successfully located the distressed aircraft. In a case where the Mayday call was falsely sent the person responsible must pay for the search and rescue operations cost and can be subject to up to 6 years in prison as well as a $250,000 fine.