JP 3-50 National Search and Rescue Manual Vol I - US Navy

451 Uncertainty Phase
An Emergency phase is said to exist when there is knowledge of a
situation that may need to be monitored, or to have more information
gathered, but that does not require moving of resources. When there is
doubt about the safety of a craft or person, or they are overdue, the
situation should be investigated and information gathered. A
preliminary communications search (PRECOM) may begin in this phase.
452 Alert Phase
An Alert phase exists when a craft or person has difficulty and may
need assistance, but is not in immediate danger or in need of immediate
response. Apprehension is usually associated with the Alert phase.
SRUs could be launched, but there is no threat requiring immediate
action. For overdues, Alert occurs when there is continued lack of
information concerning progress or position. Units should begin or
continue communications searches, and possibly dispatch SRUs to
investigate high-probability locations or overfly the craft's intended
route.
453 Distress Phase
The Distress phase exists when a craft or person is threatened by
grave or imminent danger requiring immediate response to the distress
scene. For overdues, distress exists when communications searches and
other forms of investigation have not succeeded, and search planning and
execution are needed.
454 FAA Emergency Phases
FAA emergency phase differ from the above SAR emergency phases.
The FAA uses "Information Request" (INREQ) and "Alert Notice" (ALNOT) to
indicate emergency conditions over land. INREQ, corresponding to the
SAR Uncertainty phase, is a message request for aircraft information to
FSSs along the aircraft's planned route. ALNOT, corresponding to the
SAR Alert phase, is an alerting message containing all known aircraft
data and addressed to the appropriate RCC and all aeronautical
facilities within 50 miles of the aircraft's planned route. Both INREQs
and ALNOTs must be answered within 60 minutes. In oceanic airspace, the
emergency phase terms used by the FAA are the same as those used for
SAR, but in coastal areas either terminology may be used in reporting
aircraft emergencies be to RCCs. Appropriate FAA facilities will
clarify any confusion.
460 SAR FACILITIES INITIAL ACTION
A. After the initial report of an incident is evaluated and
assigned an emergency phase, the SMC usually has one of three possible
actions:
1. Dispatch SRUs immediately, or request other facilities to take
immediate action.