Definition
An ICAO-defined emergency phase declared when apprehension exists about the safety of an aircraft and its occupants. It is the second of three escalating emergency phases used by air traffic services and search and rescue authorities, sitting between the Uncertainty Phase (Incerfa) and the Distress Phase (Detresfa).
Plain English
A formal alert level meaning controllers and search and rescue services are now genuinely worried about an aircraft. It's more serious than 'we can't reach them' but not yet 'we believe they're in danger.'
Context Anchor
Seen in air traffic control, flight service, and search-and-rescue coordination when an aircraft is missing, late, not communicating, or otherwise raising safety concerns.
Derivation
Alerfa is a contraction of 'Alert Phase,' built the same way ICAO created Incerfa (Uncertainty) and Detresfa (Distress). The shortened forms exist so the phase can be transmitted clearly over radio and teletype without confusion across languages.
Why Pilots Care
Triggers stepped-up monitoring, radio checks, and preparation for possible rescue efforts before a full distress phase is declared.
Intuition Check
Alerfa does not simply mean “be alert.” In aviation, it is a formal emergency phase showing real concern for an aircraft’s safety, one step short of confirmed distress.
Example Sentence 1
When the aircraft failed to report at its expected position and could not be raised on the radio, the controller escalated from Uncertainty Phase to Alerfa.
Example Sentence 2
Under ALERFA the rescue coordination center alerted nearby airports and requested weather and traffic information along the planned route.