MAYDAY vs PANPAN
An emergency situation is one in which the safety of the aircraft or of persons on board or on the ground is endangered for any reason.
An abnormal situation happens when it is no longer possible to continue the flight using normal procedures but the safety of the aircraft or persons on board or on the ground is not in danger.
Emergency or abnormal situations may develop as a result of one or more factors within or outside an aircraft, for example:
• Fire onboard;
• System failure or malfunction (engine failure, landing gear malfunction...);
• Shortage of fuel;
• Flight crew uncertain of position;
• Adverse weather;
• Pilot incapacitation;
• Aircraft damage;
An emergency or abnormal situation may result in it being impossible to continue the flight to destination as planned, resulting in one or more of the following outcomes:
• Loss of altitude;
• Diversion to a nearby aerodrome;
• Forced landing;
• Injuries or even deaths onboard.
Mayday is a situation that causes risk to passengers or aircraft.
Which means that if there is no help, there is a great chance of dying.
In the other hand, the PAN PAN PAN message means a situation where an emergency has happened, but it is under control and it will not put lives and aircraft at risk.