Distress, urgency and calls

DISTRESS: the radio-telephone distress signal MAYDAY is used to indicate that a vessel, aircraft or person is in grave and imminent danger and requires immediate assistance.
URGENCY: the radio-telephone urgency signal PAN PAN is used to indicate that a vessel has a very urgent message to transmit about its safety – such as loss of steering.
Distress and urgency calls and messages must be cancelled if assistance is no longer required or when the incident is over. 
In an emergency call *500 via cellphone or follow the VHF instructions