Instrument flight rules

Instrument flight rules (IFR) are regulations and procedures for conducting aircraft flights using instrument references and air traffic control clearances, particularly when visual conditions are insufficient.

Instrument meteorological conditions: Weather conditions in which visibility or cloud clearance falls below the minima for visual flight. These conditions commonly require pilots to operate under instrument flight rules.
Instrument flight: Aircraft control and navigation primarily by interpreting cockpit instruments rather than external visual references. Instrument flight is the operational practice governed by IFR rules.
Instrument departure procedure: A published route and set of instructions for aircraft departing an airport under instrument conditions. It standardizes obstacle clearance and routing immediately after an IFR takeoff.
Visual meteorological conditions: Weather conditions meeting prescribed visibility and cloud-clearance minima for visual flight. VMC may permit visual operations even when a flight could also be conducted under IFR.
Instrument flight rules flight plan: A flight plan filed for a flight conducted under instrument flight rules. It lets air traffic control plan and coordinate an IFR aircraft's route.
Instrument rating: A pilot qualification authorizing flight under instrument conditions, subject to applicable regulations. Pilots generally need this qualification to act as pilot in command on IFR flights.
Standard instrument departure: A published instrument departure route that connects an airport to the en-route air traffic system. A SID can encode the initial IFR route and climb instructions in a clearance.
Special visual flight rules: An authorization for visual flight in certain controlled airspace when ordinary VFR weather minima are not met. SVFR is a limited visual alternative, not the same operating system as IFR.
Air traffic control clearance: An authorization issued by air traffic control specifying conditions under which an aircraft may proceed. An IFR aircraft normally follows its assigned clearance through controlled airspace.
Flight instruments: Cockpit instruments that indicate an aircraft's attitude, altitude, airspeed, heading, and related flight data. They supply the information needed to control an aircraft without reliable outside visual cues.

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