Plain English Meaning

The rules pilots follow when they cannot rely on what they see outside the aircraft and must fly using their instruments instead, under the direction of air traffic control.

Full Definition

A set of regulations issued by the FAA governing flight conducted under conditions in which the pilot navigates and controls the aircraft primarily by reference to cockpit instruments rather than by outside visual reference. IFR flight requires an instrument-rated pilot, an appropriately equipped aircraft, an ATC clearance, and operation in accordance with that clearance and assigned routing.

Context Anchor

You will see this term in weather decisions, filing, air traffic control , and discussions of whether a pilot and aircraft are allowed to fly in reduced .