Plain English Meaning

The rules pilots fly under when they can't rely on seeing outside -- such as in clouds or low visibility -- and must instead fly by their instruments while following directions from air traffic control.

Full Definition

A set of FAA regulations governing the conduct of flight in instrument meteorological conditions, or any flight operating on an IFR flight plan, where the pilot navigates and controls the aircraft primarily by reference to cockpit instruments rather than visual reference to the ground or horizon. IFR operations require an IFR flight plan, an ATC clearance, and pilot and aircraft qualifications appropriate to .