(1) Mayday (distress) means that a ship or other vehicle is threatened by grave and imminent danger and requests immediate assistance.
(2) Pan Pan (urgency) means that the calling station has a very urgent message to transmit concerning the safety of a ship, aircraft or other vehicle, or of a person. (3) Securite (safety) means that the station is about to transmit a message concerning the safety of navigation or giving important meteorological warnings.
