Distress: Understanding MAYDAY

You are airborne near Koblenz. Your engine starts losing power. The vibration increases. You realize this could become serious. What you do in the next thirty seconds—what you say and how you say it—could determine whether you land safely or whether rescuers spend the next six hours searching for you.

This is the reality of distress communications. A distress situation is one where an aircraft and its occupants are threatened by grave and imminent danger and require immediate assistance. The word MAYDAY is an international distress call transmitted on a dedicated emergency frequency. In aviation, that frequency is 121.5 MHz VHF (or 243.0 MHz for military aircraft and helicopters in certain circumstances).

MAYDAY is not something you "try"—it is something you declare when the situation genuinely requires it. A genuine distress is:

Loss of engine power and inability to reach a suitable landing site
Structural damage threatening flight safety or aircraft integrity
Fire in the aircraft
Loss of all radio communication (in some circumstances, though see radio failure procedures below)
Medical emergency where the pilot is unable to continue flying
Fuel emergency: insufficient fuel to reach any aerodrome
Decompression or rapid altitude loss
Uncontrolled descent toward terrain
Complete loss of navigation capability with land-sea uncertainty in bad weather

If any of these occur, you declare MAYDAY immediately. Do not wait. Do not hesitate. The sooner ATC and rescue services know, the better they can help.