Three emergency phases into which an incident may be classified or progress, according to the seriousness of the incident and its requirement for rescue service. A. Uncertainty phase — Doubt exists as to the safety of a craft or person because of knowledge of possible difficulties or because of lack of information concerning progress or position. B. Alert phase — Apprehension exists for the safety of a craft or person because of definite information that serious difficulties exist that do not amount to a distress or because of a continued lack of information concerning progress or position. C. Distress phase — Immediate assistance is required by a craft or person because of being threatened by grave or imminent danger or because of continued lack of information concerning progress or position after procedures for the alert phase have been executed.