Definition
A set of FAA regulations governing flight conducted primarily by reference to the aircraft's instruments rather than by outside visual reference. IFR flight requires an instrument-rated pilot, an appropriately equipped aircraft, an ATC clearance, and operation within the air traffic control system. IFR rules apply when weather conditions are below the minimums required for visual flight, and pilots may also elect to fly IFR in good weather.
Plain English
A way of flying where the pilot controls the aircraft using the cockpit instruments and follows instructions from air traffic control, instead of looking out the window to navigate. It's the system used when clouds, low visibility, or pilot choice make instrument flying necessary.
Context Anchor
You will see IFR in weather briefings, flight plans, clearances, training records, and discussions about whether a pilot and aircraft are allowed to fly in poor visibility.
Derivation
Instrument' refers to the cockpit gauges and displays the pilot uses to know the aircraft's attitude, altitude, heading, and position. 'Flight Rules' refers to the body of FAA regulations governing how the flight is conducted. Together, the term names the rule set that applies when flying primarily by reference to instruments.
Why Pilots Care
Determines whether an IFR clearance is required, what aircraft equipment and pilot ratings are needed, and how the flight is conducted for safety in poor weather.
Intuition Check
IFR does not simply mean “bad weather flying.” A flight can be IFR in clear weather if it is planned and conducted under Instrument Flight Rules.
Example Sentence 1
The pilot filed IFR for the cross-country because a layer of clouds was forecast along the route.
Example Sentence 2
ATC issued an IFR clearance that allowed the aircraft to climb through the clouds on instruments.