Plain English Meaning

These are extra reports a pilot must give to air traffic control on their own initiative, without being asked, whenever certain things happen during the flight that controllers need to know about.

Full Definition

Position or status reports that a pilot is required to make to ATC without a specific request, in addition to the routine reports already required by regulation or clearance. They cover events such as a change in true airspeed, vacating an assigned altitude, an inability to climb or descend at 500 feet per minute, missed approaches, loss of navigation capability, weather encounters, and similar conditions that affect the safe or expected progress of the flight.