Definition
Position, status, or condition reports that pilots are required to make to Air Traffic Control under specified circumstances during IFR flight. Some reports are mandatory at all times (such as leaving an assigned altitude, unforecast weather, or equipment malfunctions), while others are required only when not in radar contact (such as reaching a reporting fix or estimating arrival times).
Plain English
These are the updates pilots must give to controllers during an instrument flight. Some you always have to make; others you only make when ATC is not watching you on radar.
Context Anchor
You encounter ATC reports during IFR en route flying, holding, altitude changes, missed approaches, and any time ATC needs pilot-provided information to maintain a safe traffic picture.
Derivation
Report comes from older Latin roots meaning “to carry back.” That fits the aviation use: the pilot carries information back to air traffic control so the controller can make safe decisions.
Why Pilots Care
Maintains traffic separation and regulatory compliance, preventing loss of separation or airspace violations.
Intuition Check
Do not think of a report here as a written paper or a long explanation. In ATC use, a report is usually a short, timely radio update that gives the controller a needed fact.
Example Sentence 1
After climbing through a layer of unforecast icing, the pilot made one of the required ATC reports to advise the controller of the conditions.
Example Sentence 2
After leveling at the assigned altitude, the crew transmitted their ATC report confirming the altitude change.