Definition
A set of FAA regulations governing flight conducted primarily by reference to cockpit instruments rather than outside visual cues. IFR operations require an instrument-rated pilot, an appropriately equipped aircraft, an ATC clearance, and adherence to instrument procedures for departure, en route navigation, approach, and landing. IFR is used in instrument meteorological conditions (IMC) and is also commonly used in visual conditions for the structure and traffic separation it provides.
Plain English
The rules a pilot follows when flying mainly by looking at the instruments instead of out the window. ATC tells the pilot what altitude to fly and what route to take, and the pilot follows published procedures for taking off, navigating, and landing.
Context Anchor
You will see IFR in airspace rules, weather minimums, flight plans, air traffic control clearances, and instrument training.
Derivation
Instrument comes from a Latin word meaning a tool or device. In aviation, the instruments are the cockpit displays and gauges that let the pilot control and navigate the aircraft when looking outside is not enough. IFR is simply the shortened form of instrument flight rules.
Why Pilots Care
Determines whether a flight can proceed in marginal weather, which routes and altitudes are available, and whether an instrument approach or departure procedure will be needed.
Grounding Statement
Picture flying inside a cloud: there may be nothing useful to see outside, so the pilot must use the instruments and follow the IFR system.
Intuition Check
IFR does not mean “bad weather.” It means a rule set for flying by instruments and required procedures; a flight can be IFR even when the weather is clear.
Example Sentence 1
Because the destination was forecasting low clouds and rain, she filed an IFR flight plan before departure.
Example Sentence 2
Under instrument flight rules the controller issued a heading to intercept the final approach course.