The first paragraph of the regulation states “The pilot in command of each aircraft operated in controlled airspace under IFR shall report as soon as practical to ATC any malfunctions of navigational, approach, or communication equipment occurring in flight.” The next paragraph tells us what needs to be in our report: ...

Under 2026 FAA regulations (specifically 14 CFR 91.183 and 91.187), a pilot operating under Instrument Flight Rules (IFR) must make several mandatory reports to Air Traffic Control (ATC) without being asked. These include: (1) Vacating any previously assigned altitude for a newly assigned one; (2) Altitude change if operating on a "VFR-on-top" clearance; (3) Inability to climb or descend at at least 500 feet per minute; (4) Missed approach (requesting instructions for the next move); (5) Change in average true airspeed (at cruise) when it varies by 5% or 10 knots (whichever is greater) from the filed flight plan; (6) Time and altitude reaching a holding fix or point to which cleared; (7) Leaving any assigned holding fix or point; and (8) Any loss of navigational, approach, or communication capability. In a "non-radar" environment, pilots must also report reaching designated "compulsory" reporting points. Furthermore, any information regarding hazardous weather or safety of flight must be reported immediately. These requirements ensure that controllers can maintain proper separation and situational awareness in an environment where pilots cannot rely on "see and avoid" visual techniques.