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IFR - Instrument Flight Rules, governing flight under instrument meteorological conditions.

IFR CONDITIONS - weather conditions below the minimum for flight under visual flight rules.

IFR OVER-THE-TOP - with respect to the operation of aircraft, means the operation of an aircraft over-the-top on an IFR flight plan when cleared by air traffic control to maintain "VFR conditions" or "VFR conditions on top".

ILS - Instrument Landing System.

INCIDENT - An occurrence other than an accident associated with the operation of an aircraft, which affects or could affect the safety of operations.

INDICATED AIRSPEED (IAS) - A direct instrument reading obtained from an airspeed indicator uncorrected for altitude, temperature, atmospheric density or instrument error.

INSTRUMENT - A device using an internal mechanism to show visually or aurally the attitude, altitude, or operation of an aircraft or aircraft part. It includes electronic devices for automatically controlling an aircraft in flight.

INSTRUMENT APPROACH PROCEDURE (IAP) - series of predetermined maneuvers by reference to flight instruments with specified protection from obstacles and assurance of navigation signal reception capability. It begins from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point: (1) From which a landing can be completed; or (2) If a landing is not completed, to a position at which holding or en route obstacle clearance criteria apply.

INTERSTATE AIR COMMERCE - The carriage by aircraft of persons or property for compensation or hire, or the carriage of mail by aircraft, or the operation or navigation of aircraft in the conduct or furtherance of a business or vocation, in commerce between a place in any State of the United States, or the District of Columbia, and a place in any other State of the United States, or the District of Columbia; or between places in the same State of the United States through the airspace over any place outside thereof; or between places in the same territory or possession of the United States, or the District of Columbia.

INTERSTATE AIR TRANSPORTATION - The carriage by aircraft of persons or property as a common carrier for compensation or hire, or the carriage of mail by aircraft in commerce: (1) Between a place in a State or the District of Columbia and another place in another State or the District of Columbia; (2) Between places in the same State through the airspace over any place outside that State; or (3) Between places in the same possession of the United States; whether that commerce moves wholly by aircraft of partly by aircraft and partly by other forms of transportation.

INTRASTATE AIR TRANSPORTATION - The carriage of persons or property as a common carrier for compensation or hire, by turbojet-powered aircraft capable of carrying thirty or more persons, wholly within the same State of the United States.