Warning: The following audio content may not be suitable for all listeners. It involves life and death radio transmissions that some listeners might find disturbing.
A Mayday radio call should be reserved for life threatening situations. These may include, but are not limited to:
- Loss, or imminent loss of aircraft control for any number of different reasons
- aircraft upset by turbulence;
- pilot incapacitation;
- control surface or structural failure;
- engine failure leading to a forced landing/ditching/ejection/bailout;
spatial disorientation, etc.
- Or, an onboard fire.
Here are two recordings, released by the F.A.A., of Mayday radio transmissions, along with the response by air traffic control.
This is what the Aeronautical Information Manual has to say about using Mayday on the radio.
6-3-1
c. The initial communication, and if considered necessary, any subsequent transmissions by an aircraft in distress should begin with the signal MAYDAY, preferably repeated three times. The signal PAN-PAN should be used in the same manner for an urgency condition.
d. Distress communications have absolute priority over all other communications, and the word MAYDAY commands radio silence on the frequency in use. Urgency communications have priority over all other communications except distress, and the word PAN-PAN warns other stations not to interfere with urgency transmissions.
Note the difference between Mayday and Pan-Pan. Mayday commands radio silence. No other pilots or controllers should speak while the distress situation is under way. Pan-pan gives the pilot in an urgent situation top priority on the radio. Other conversations may continue as long as they do not interfere with communication between the pilot making the Pan-Pan call, and the agency contracted.