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

C. An aircraft SAR incident is considered probable or actual when:
1. An aircraft requests assistance or transmits a distress
signal.
2. Aircraft ditching, crash, or forced landing is actual or
imminent.
3. The crew is about to abandon, or has abandoned the aircraft.
4. Unlawful aircraft interference is known or believed.
5. The aircraft is overdue and one of the following conditions
exists:
a. If the aircraft is on an IFR flight plan, neither
communications nor radar contact can be established and 30
minutes have passed since its ETA over a reporting point or at
a clearance limit.
b. If the aircraft is on a VFR flight plan,
communications cannot be established and it fails to arrive 30
minutes after its ETA.
c. If the aircraft is not on a flight plan, a reliable
source reports it 1 hour overdue at its destination.
d. If cleared to land, the aircraft fails to land within
5 minutes of ETA and communications have not been
reestablished.
e. If, in certain areas of the United States, the
aircraft is not in compliance with special reporting and
flight-following service criteria established by FAA FSSs.
Commonly these are areas where critical survival factors make
earlier activation of the SAR system desirable. FAA
publications should be consulted for details of these special
services, and liaison maintained with FAA Regional and Area
authorities.
D. A submersible water craft incident is considered probable or
actual when:
1. For Navy submarines, the operating authority declares an
emergency phase. The two phases an emergency are EVENT
SUBMISS, the initial search stage, and EVENT SUBSUNK, the
full-scale search. Specialized Navy SAR organization and
facilities are established for Navy submarines.
2. For civilian submersibles
a. A submersible fails to surface promptly following a
known accident, or an accident report has been received from