(2)
United States military Standard Instrument Approach Procedures are approved and published by the Department of Defense.

(3)
Special Instrument Approach Procedures are approved by the Federal Aviation Administration for individual operators, but are not published in Federal Air Regulations, Part 97, for public use.

INSTRUMENT APPROACH PROCEDURE (JCS, NATO) - 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 or the Missed Approach Procedure is initiated.
INSTRUMENT APPROACH PROCEDURE (ICAO) - A series of predetermined maneuvers by reference to flight instruments with specified protection from obstacles from the Initial Approach Fix, or where applicable, from the beginning of a defined arrival route to a point from which a landing can be completed and thereafter, if a landing is not completed, to a position at which holding or enroute obstacle clearance criteria apply.
INSTRUMENT DEPARTURE PROCEDURE (DP) (P/CG) - A preplanned instrument flight rule (IFR) air traffic control departure procedure printed for pilot use in graphic and/or textual form. DP's provide transition from the terminal to the appropriate enroute structure.

INSTRUMENT FLIGHT RULES/IFR (P/CG) - Rules governing the procedures for conducting instrument flight. Also a term used by pilots and controllers to indicate type of flight plan. (See Visual Flight Rules, Instrument Meteorological Conditions, Visual Meteorological Conditions)
INSTRUMENT FLIGHT RULES (ICAO) - A set of rules governing the conduct of flight under Instrument Meteorological Conditions.
INSTRUMENT LANDING SYSTEM/ILS (P/CG) - A precision instrument approach system which normally consists of the following electronic components and visual aids.
(1)
LOCALIZER (See Localizes)

(2)
GLIDE SLOPE (See Glide Slope)

(3)
OUTER MARKER (See Outer Marker)

(4)
MIDDLE MARKER (See Middle Marker)

(5)
APPROACH LIGHTS (See Airport Lighting)

(Refer to Federal Air Regulations Part 91)
INSTRUMENT LANDING SYSTEM (JCS, NATO) - A system of radio navigation intended to assist aircraft in landing which provides lateral and vertical guidance, including indications of distance from the optimum point of landing.
INSTRUMENT METEOROLOGICAL CONDITIONS-IMC (P/CG, ICAO) - Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling less than the minima specified for Visual Meteorological Conditions. (See Visual Meteorological Conditions, Instrument Flight Rules, Visual Flight Rules)
INSTRUMENT RUNWAY (P/CG) - A runway equipped with electronic and visual navigation aids for which a precision or non precision approach procedure having straight-in landing minimums has been approved.