It is a signal to indicate that they are in imminent danger and require immediate assistance. When a pilot makes a Mayday call, it is typically directed to the nearest air traffic control (ATC) facility for help. The Mayday call will include the following information:
The word "Mayday" is spoken three times
The call sign or registration of the aircraft
The nature of the emergency
The location and position of the aircraft
The number of people on board
Any other relevant information, such as the condition of the crew.
A typical Mayday call would sound like this:
"Mayday, Mayday, Mayday, this is flight XYZ; we have an engine failure, and our position is Lat: XX.XXXX, Long: XX.XXXX, We are carrying XX passengers and crew; we need immediate assistance."
The Mayday call is the highest priority and will take precedence over all other radio traffic. Air traffic controllers will immediately give priority to the Mayday aircraft. They will clear the airspace around the aircraft to ensure that it can make an emergency descent or landing safely.
It's important to note that Mayday calls should only be made in genuine emergencies, as a false Mayday call is a serious offense and can divert emergency services from real emergencies. Pilots are trained to identify and handle emergencies and only make a Mayday call when necessary.