AIM 8/15/19 12/31/20 Appendix 3 − 3 Abbreviations/Acronyms Abbreviation/ Acronym Meaning LLWAS − RS . Low Level Wind Shear Alert System Relocation/Sustainment LNAV...... Lateral Navigation LOC ....... Localizer LOP ....... Line − of − position LORAN .... Long Range Navigation System LP......... Localizer Performance LPV ....... Localizer Performance with Vertical Guidance LUAW ..... Line Up and Wait LZ......... Landing Zone MAHWP . . . Missed Approach Holding Waypoint MAP....... Missed Approach Point MAWP ..... Missed Approach Waypoint MDA ...... Minimum Descent Altitude MEA....... Minimum En Route Altitude MEARTS . . . Micro En Route Automated Radar Tracking System METAR .... Aviation Routine Weather Report MHz ....... Megahertz MIRL ...... Medium Intensity Runway Lights MM ....... Middle Marker MOA ...... Military Operations Area MOCA ..... Minimum Obstruction Clearance Altitude MRA ...... Minimum Reception Altitude MRB....... Magnetic Reference Bearing MSA....... Minimum Safe Altitude MSAW ..... Minimum Safe Altitude Warning MSL ....... Mean Sea Level MTI ....... Moving Target Indicator MTOS...... Mountain Obscuration MTR....... Military Training Route MVA....... Minimum Vectoring Altitude MWA ...... Mountain Wave Activity MWO ...... Meteorological Watch Office NAS ....... National Airspace System NASA ...... National Aeronautics and Space Administration NAVAID.... Navigational Aid NAVCEN . . . Coast Guard Navigation Center NCWF ..... National Convective Weather Forecast NDB ....... Nondirectional Radio Beacon NEXRAD . . . Next Generation Weather Radar NFDC ...... National Flight Data Center NGA....... National Geospatial − Intelligence Agency NM ........ Nautical Mile NMAC ..... Near Midair Collision Abbreviation/ Acronym Meaning NOAA ..... National Oceanic and Atmospheric Administration NOPAC .... North Pacific NoPT ...... No Procedure Turn Required NPA ....... Nonprecision Approach NRS ....... Navigation Reference System NSA ....... National Security Area NSW....... No Significant Weather NTSB ...... National Transportation Safety Board NTZ ....... No Transgression Zone NWS....... National Weather Service OAT ....... Outside Air Temperature OBS ....... Omni − bearing Selector ODP ....... Obstacle Departure Procedure OIS ........ Operational Information System OIS ........ Obstacle Identification Surface OM ........ Outer Marker ORD ....... Chicago O’Hare International Airport PA......... Precision Approach PAPI ....... Precision Approach Path Indicator PAR ....... Precision Approach Radar PAR ....... Preferred Arrival Route PC......... Personal Computer P/CG ....... Pilot/Controller Glossary PDC ....... Pre − departure Clearance PFD ....... Personal Flotation Device PinS ....... Point − in − Space PIREP ...... Pilot Weather Report POB ....... Persons on Board POFZ ...... Precision Obstacle Free Zone POI ........ Principal Operations Inspector PPS........ Precise Positioning Service PRM ....... Precision Runway Monitor PT......... Procedure Turn QICP ...... Qualified Internet Communications Provider RA ........ Resolution Advisory RAA ....... Remote Advisory Airport RAIM ...... Receiver Autonomous Integrity Monitoring RAIS ...... Remote Airport Information Service RBDT ...... Ribbon Display Terminals RCAG ..... Remote Center Air/Ground RCC ....... Rescue Coordination Center RCLS ...... Runway Centerline Lighting System RCO ....... Remote Communications Outlet TAF ....... Aerodrome Forecast RD ........ Rotor Diameter