IF/IAWP- Intermediate Fix/Initial Approach Way‐point. The waypoint where the final approach course of a T approach meets the crossbar of the T. When designated (in conjunction with a TAA) this waypoint will be used as an IAWP when approaching the airport from certain directions, and as an IFWP when beginning the approach from another IAWP.
IFWP- Intermediate Fix Waypoint
ILS-
(See INSTRUMENT LANDING SYSTEM.)
ILS CATEGORIES-1. ILS Category I. An ILS approach procedure which provides for approach to a height above touchdown of not less than 200 feet and with runway visual range of not less than 1,800 feet.- 2. ILS Category II. An ILS 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 1,200 feet.- 3. ILS Category III:
a.
IIIA.-An ILS 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 ILS 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 ILS approach procedure which provides for approach without a decision height minimum and without runway visual range minimum.
ILS PRM APPROACH-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.
IM-(See INNER MARKER.)
IMC-
(See INSTRUMENT METEOROLOGICAL
CONDITIONS.)

IMMEDIATELY- Used by ATC or pilots when such action compliance is required to avoid an imminent situation.
INCERFA (Uncertainty Phase) [ICAO]- A situation wherein uncertainty exists as to the safety of an aircraft and its occupants.

INCREASE SPEED TO (SPEED)-
(See SPEED ADJUSTMENT.)
INERTIAL NAVIGATION SYSTEM- An RNAV system which is a form of self‐contained navigation.
(See Area Navigation/RNAV.)
INFLIGHT REFUELING-
(See AERIAL REFUELING.)
INFLIGHT WEATHER ADVISORY-
(See WEATHER ADVISORY.)
INFORMATION REQUEST- A request originated by an FSS for information concerning an overdue VFR aircraft.
INITIAL APPROACH FIX- The fixes depicted on instrument approach procedure charts that identify the beginning of the initial approach segment(s).
(See FIX.)
(See SEGMENTS OF AN INSTRUMENT
APPROACH PROCEDURE.)

INITIAL APPROACH SEGMENT-
(See SEGMENTS OF AN INSTRUMENT
APPROACH PROCEDURE.)

INITIAL APPROACH SEGMENT [ICAO]- That segment of an instrument approach procedure between the initial approach fix and the intermediate approach fix or, where applicable, the final approach fix or point.
INLAND NAVIGATION FACILITY- A navigation aid on a North American Route at which the common route and/or the noncommon route begins or ends.