(2)
Instrument Landing System CATEGORY II - An Instrument Landing System approach procedure which provides for approach to a Height Above Touchdown of not less than 100 feet and with Runway Visual Range of not less than 1200 feet.

(3) Instrument Landing System CATEGORY III.

(a)
IIIA - An Instrument Landing System approach procedure which provides for approach without a Decision Height minimum and with Runway Visual Range of not less than 700 feet.

(b)
IIIB - An Instrument Landing System approach procedure which provides for approach without a Decision Height minimum and with Runway Visual Range of not less than 150 feet.

(c)
IIIC - An Instrument Landing System approach procedure which provides for approach without a Decision Height minimum and without Runway Visual Range minimum.

ILS PRM APPROACH (P/CG) - An instrument landing system (ILS) approach conducted to parallel runways whose extended centerlines are separated by less than 4,300 feet and the parallel runways have a Precision Runway Monitoring (PRM) system that permits simultaneous independent ILS approaches.
IMMEDIATELY - Used by Air Traffic Control when such action is required to avoid an imminent situation.
INCREASE SPEED TO (SPEED) - (See Speed Adjustment) INDIVIDUAL FLIGHT PLAN FROM THIS POINT/IFPFP (USAF) - The point at which the aircraft flying the route will proceed on an individual flight plan to the destination.
INFORMATION REQUEST/INREQ - A request originated by a Flight Service Station for information concerning an overdue Visual Flight Rules aircraft.
INITIAL APPROACH FIX/IAF - The fix(s) depicted on Instrument Approach Procedure charts that identifies the beginning of the initial approach segments(s). (See Fix, Segments of an Instrument Approach Procedure)
INITIAL APPROACH SEGMENT - (See Segments of an Instrument Approach Procedure)
INNER MARKER/IM/INNER MARKER BEACON - A marker beacon used with an Instrument Landing System (Category II) precision approach located between the Middle Marker and the end of the Instrument Landing System runway, transmitting a radiation pattern keyed at six dots per second and indicating to the pilot, both aurally and visually, that he is at the designated Decision Height (DH), normally 100 feet above the Touchdown Zone Elevation, on the Instrument Landing System Category II approach. It also marks progress during a Category III approach. (See Instrument Landing System)
INSTRUMENT APPROACH PROCEDURE/IAP/INSTRUMENT APPROACH (P/CG) - A series of predetermined maneuvers for the orderly transfer of an aircraft under instrument flight conditions from the beginning of the initial approach to a landing, or to a point from which a landing may be made visually. It is prescribed and approved for a specific airport by competent authority. (See Segments of an Instrument Approach Procedure) (Refer to Federal Air Regulations Part 91)