47 CFR 80.91 - Order of priority of communications.
(a) All stations in the maritime mobile service and the maritime mobile-satellite service shall be capable of offering four levels of priority in the following order:
(1) Distress calls, distress messages, and distress traffic.
(2) Urgency communications.
(3) Safety communications.
(4) Other communications.
(b) In a fully automated system, where it is impracticable to offer all four levels of priority, category 1 shall receive priority until such time as intergovernmental agreements remove exemptions granted for such systems from offering the complete order of priority.