Mayday Threshold

Build the decision around four questions: Is a vessel or person in grave danger? Is the danger imminent rather than merely possible? Is immediate outside assistance required? Would delaying the alert materially reduce the chance of a safe response? The MCA threshold supplies the first three; the fourth is a practical check against waiting until the last possible moment.

Some incidents change category. A controllable engine failure in safe water may be routine or urgency. The same failure with a lee shore close aboard and no remaining means of arrest can become distress. A medical incident may begin as PAN-PAN for advice and become Mayday if the person's condition becomes immediately life-threatening and urgent rescue is required.

Do not downgrade because the crew has also activated a beacon, made a phone call or attracted a nearby vessel. Parallel alerting may help, but the Mayday voice message broadcasts locally, establishes distress traffic and provides details. Conversely, a Mayday does not relieve the skipper of collision avoidance, damage control, lifejacket, abandonment or recovery decisions.