A topA/C -- AircraftA/G -- Air to GroundA/H -- Altitude/HeightAAC -- Mike Monroney Aeronautical CenterAAF -- Army Air FieldAAI -- Arrival Aircraft IntervalAAP -- Advanced Automation ProgramAAR -- Airport Acceptance RateABDIS -- Automated Data Interchange System Service BACAIS -- Air Carrier Activity Information SystemACAS -- Aircraft Collision Avoidance SystemACC -- Airports Consultants CouncilACC -- Area Control CenterACCT -- Accounting RecordsACD -- Automatic Call DistributorACDO -- Air Carrier District OfficeACF -- Area Control FacilityACFO -- Aircraft Certification Field OfficeACFT -- AircraftACI-NA -- Airports Council International - North AmericaACID -- Aircraft IdentificationACIP -- Airport Capital Improvement PlanACLS -- Automatic Carrier Landing SystemACLT -- Actual Landing Time CalculatedACO -- Office of Airports Compliance and Field OperationsACO -- Aircraft Certification OfficeACRP -- Airport Cooperative Research ProgramADA -- Air Defense AreaADAP -- Airport Development Aid ProgramADAS -- AWOS Data Acquisition SystemADCCP -- Advanced Data Communications Control ProcedureADDA -- Administrative DataADF -- Automatic Direction FindingADI -- Automatic De-Ice and InhibitorADIN -- AUTODIN ServiceADIZ -- Air Defense Identification ZoneADL -- Aeronautical Data-LinkADLY -- Arrival DelayADO -- Airline Dispatch OfficeADP -- Automated Data ProcessingADS -- Automatic Dependent SurveillanceADSIM -- Airfield Delay Simulation ModelADSY -- Administrative Equipment SystemsADTN -- Administrative Data Transmission NetworkADTN2000 -- Administrative Data Transmission Network 2000 ADVO -- Administrative VoiceAEG -- Aircraft Evaluation GroupAERA -- Automated En-Route Air Traffic ControlAEX -- Automated ExecutionAF -- Airway FacilitiesAFB -- Air Force BaseAFIS -- Automated Flight Inspection SystemAFP -- Area Flight PlanAFRES -- Air Force Reserve StationAFS -- Airways Facilities SectorAFSFO -- AFS Field OfficeAFSFU -- AFS Field UnitAFSOU -- AFS Field Office Unit (Standard is AFSFOU)AFSS -- Automated Flight Service StationAFTN -- Automated Fixed Telecommunications NetworkAGIS -- Airports Geographic Information SystemAGL -- Above Ground LevelAID -- Airport Information DeskAIG -- Airbus Industries GroupAIM -- Airman's Information ManualAIP -- Airport Improvement PlanAIRMET -- Airmen's Meteorological InformationAIRNET -- Airport Network Simulation ModelAIS -- Aeronautical Information ServiceAIT -- Automated Information TransferALP -- Airport Layout PlanALS -- Approach Lighting SystemALSF1 -- ALS with Sequenced Flashers IALSF2 -- ALS with Sequenced Flashers IIALSIP -- Approach Lighting System Improvement Plan ALTRV -- Altitude ReservationAMASS -- Airport Movement Area Safety SystemAMCC -- ACF/ARTCC Maintenance Control CenterAMOS -- Automated Meteorological Observation Station AMP -- ARINC Message Processor (OR) Airport Master Plan AMVER -- Automated Mutual Assistance Vessel Rescue System ANC -- Alternate Network ConnectivityANCA -- Airport Noise and Capacity ActANG -- Air National GuardANGB -- Air National Guard BaseANMS -- Automated Network Monitoring SystemANSI -- American National Standards GroupAOA -- Air Operations AreaAP -- Acquisition PlanAPP -- ApproachAPS -- Airport Planning StandardAQAFO -- Aeronautical Quality Assurance Field Office ARAC -- Army Radar Approach Control (AAF)ARAC -- Aviation Rulemaking Advisory CommitteeARCTR -- FAA Aeronautical Center or AcademyARF -- Airport Reservation FunctionARFF -- Aircraft Rescue and Fire FightingARINC -- Aeronautical Radio, Inc.ARLNO -- Airline OfficeARO -- Airport Reservation OfficeARP -- Airport Reference PointARRA -- American Recovery and Reinvestment Act of 2009 ARSA -- Airport Service Radar AreaARSR -- Air Route Surveillance RadarARTCC -- Air Route Traffic Control CenterARTS -- Automated Radar Terminal SystemASAS -- Aviation Safety Analysis SystemASC -- AUTODIN Switching CenterASCP -- Aviation System Capacity PlanASD -- Aircraft Situation DisplayASDA -- Accelerate -- Stop Distance AvailableASLAR -- Aircraft Surge Launch And RecoveryASM -- Available Seat MileASP -- Arrival Sequencing ProgramASOS -- Automatic Surface Observation SystemASQP -- Airline Service Quality PerformanceASR -- Airport Surveillance RadarASTA -- Airport Surface Traffic AutomationASV -- Airline Schedule VendorAT -- Air TrafficATA -- Air Transport Association of AmericaATAS -- Airspace and Traffic Advisory ServiceATCAA -- Air Traffic Control Assigned AirspaceAT&T -- American Telephone and TelegraphAT&T ASDC -- AT&T Agency Service Delivery CenterAT&T CSA -- AT&T Customer Support AssociateATC -- Air Traffic ControlATCBI -- Air Traffic Control Beacon IndicatorATCCC -- Air Traffic Control Command CenterATCO -- Air Taxi Commercial OperatorATCRB -- Air Traffic Control Radar BeaconATCRBS -- Air Traffic Control Radar Beacon SystemATCSCC -- Air Traffic Control Systems Command CenterATCT -- Airport Traffic Control TowerATIS -- Automated Terminal Information ServiceATISR -- ATIS RecorderATM -- Air Traffic ManagementATM -- Asynchronous Transfer ModeATMS -- Advanced Traffic Management SystemATN -- Aeronautical Telecommunications NetworkATODN -- AUTODIN Terminal (FUS)ATOVN -- AUOTVON (Facility)ATOMS -- Air Traffic Operations Management SystemATS -- Air Traffic ServiceATSCCP -- ATS Contingency Command PostATTIS -- AT&T Information SystemsAUTODIN -- DoD Automatic Digital NetworkAUTOVON -- DoD Automatic Voice NetworkAVON -- AUTOVON ServiceAVN -- Aviation Standards National Field Office, Oklahoma CityAWIS -- Airport Weather InformationAWOS -- Automated Weather Observation SystemAWP -- Aviation Weather ProcessorAWPG -- Aviation Weather Products GeneratorAWS -- Air Weather StationB topBANS -- BRITE Alphanumeric SystemBART -- Billing Analysis Reporting Tool (GSA software tool)BASIC -- Basic Contract Observing StationBASOP -- Military Base OperationsBCA -- Benefit/Cost AnalysisBCR -- Benefit/Cost RatioBDAT -- Digitized Beacon DataBMP -- Best Management PracticesBOC -- Bell Operating Companybps -- bits per secondBRI -- Basic Rate InterfaceBRITE -- Bright Radar Indicator Terminal EquipmentBRL -- Building Restriction LineBUEC -- Back-- up Emergency CommunicationsBUECE -- Back-- up Emergency Communications EquipmentC topCAA -- Civil Aviation AuthorityCAA -- Clean Air ActCAB -- Civil Aeronautics BoardCARF -- Central Altitude Reservation FacilityCASFO -- Civil Aviation Security OfficeCAT -- CategoryCAT -- Clear -- Air TurbulenceCAU -- Crypto Ancillary UnitCBI -- Computer Based InstructionCCC -- Communications Command CenterCCCC -- Staff CommunicationsCCCH -- Central Computer Complex HostCC&O -- Customer Cost and ObligationCCSD -- Command Communications Service DesignatorCCS7-- NI -- Communication Channel Signal-7 -- Network Interconnect CCU -- Central Control UnitCD -- Common DigitizerCDR -- Cost Detail ReportCDT -- Controlled Departure TimeCDTI -- Cockpit Display of Traffic InformationCENTX -- Central Telephone ExchangeCEP -- Capacity Enhancement ProgramCEQ -- Council on Environmental QualityCERAP -- Center Radar Approach ControlCERAP -- Central Radar ApproachCERAP -- Combined Center/Radar Approach ControlCFC -- Central Flow ControlCFCF -- Central Flow Control FacilityCFCS -- Central Flow Control ServiceCFR -- Code of Federal RegulationsCFWP -- Central Flow Weather ProcessorCFWU -- Central Flow Weather UnitCGAS -- Coast Guard Air StationCLC -- Course Line ComputerCLIN -- Contract Line ItemCLT -- Calculated Landing TimeCM -- Commercial Service AirportCNMPS -- Canadian Minimum Navigation Performance Specification Airspace CNS -- Consolidated NOTAM SystemCNSP -- Consolidated NOTAM System ProcessorCO -- Central OfficeCOE -- U.S. Army Corps of EngineersCOMCO -- Command Communications OutletCONUS -- Continental United StatesCORP -- Private Corporation other than ARINC or MITRECPE -- Customer Premise EquipmentCPMIS -- Consolidated Personnel Management Information SystemCRA -- Conflict Resolution AdvisoryCRDA -- Converging Runway Display AidCRT -- Cathode Ray TubeCSA -- Communications Service AuthorizationCSIS -- Centralized Storm Information SystemCSO -- Customer Service OfficeCSR -- Communications Service RequestCSS -- Central Site SystemC/S/S/N -- Capacity/Safety/Security/NoiseCTA -- Controlled Time of ArrivalCTA -- Control AreaCTA/FIR -- Control Area/Flight Information RegionCTAF -- Common Traffic Advisory FrequencyCTAS -- Center -- Tracon Automation SystemCTMA -- Center Traffic Management AdvisorCUPS -- Consolidated Uniform Payroll SystemCVFR -- Controlled Visual Flight RulesCVTS -- Compressed Video Transmission ServiceCW -- Continuous WaveCWSU -- Central Weather Service UnitCWY -- ClearwayD topDA -- Direct AccessDA -- Decision Altitude/Decision HeightDA -- Descent AdvisorDABBS -- DITCO Automated Bulletin Board SystemDAIR -- Direct Altitude and Identity ReadoutDAR -- Designated Agency RepresentativeDARC -- Direct Access Radar ChanneldBA -- Decibels A-weightedDBCRC -- Defense Base Closure and Realignment CommissionDBE -- Disadvantaged Business EnterpriseDBMS -- Data Base Management SystemDBRITE -- Digital Bright Radar Indicator Tower EquipmentDCA -- Defense Communications AgencyDCAA -- Dual Call, Automatic Answer DeviceDCCU -- Data Communications Control UnitDCE -- Data Communications EquipmentDDA -- Dedicated Digital AccessDDD -- Direct Distance DialingDDM -- Difference in Depth of ModulationDDS -- Digital Data ServiceDEA -- Drug Enforcement AgencyDEDS -- Data Entry and Display SystemDEIS -- Draft Environmental Impact StatementDEP -- DepartureDEWIZ -- Distance Early Warning Identification ZoneDF -- Direction FinderDFAX -- Digital FacsimileDFI -- Direction Finding IndicatorDGPS -- Differential Global Positioning Satellite (System)DH -- Decision HeightDID -- Direct Inward DialDIP -- Drop and Insert PointDIRF -- Direction FindingDITCO -- Defense Information Technology Contracting Office Agency DME -- Distance Measuring EquipmentDME/P -- Precision Distance Measuring EquipmentDMN -- Data Multiplexing NetworkDNL -- Day-- Night Equivalent Sound Level (Also called Ldn)DOD -- Direct Outward DialDoD -- Department of DefenseDOI -- Department of InteriorDOS -- Department of StateDOT -- Department of TransportationDOTS -- Dynamic Ocean Tracking SystemDOTCC -- Department of Transportation Computer CenterDSCS -- Digital Satellite Compression ServiceDSUA -- Dynamic Special Use AirspaceDTS -- Dedicated Transmission ServiceDUAT -- Direct User Access TerminalDVFR -- Defense Visual Flight RulesDVFR -- Day Visual Flight RulesDVOR -- Doppler Very High Frequency Omni-- Directional RangeDYSIM -- Dynamic SimulatorE topE-MSAW -- En-Route Automated Minimum Safe Altitude WarningEA -- Environmental AssessmentEARTS -- En Route Automated Radar Tracking SystemECOM -- En Route CommunicationsECVFP -- Expanded Charted Visual Flight ProceduresEDCT -- Expedite Departure PathEFAS -- En Route Flight Advisory ServiceEFC -- Expect Further ClearanceEFIS -- Electronic Flight Information SystemsEIAF -- Expanded Inward Access FeaturesEIS -- Environmental Impact StatementELT -- Emergency Locator TransmitterELWRT -- ElectrowriterEMAS -- Engineered Materials Arresting SystemEMPS -- En Route Maintenance Processor SystemEMS -- Environmental Management SystemENAV -- En Route Navigational AidsEPA -- Environmental Protection AgencyEPS -- Engineered Performance StandardsEOF -- Emergency Operating FacilityEPSS -- Enhanced Packet Switched ServiceERAD -- En Route Broadband RadarESEC -- En Route Broadband Secondary RadarESP -- En Route Spacing ProgramESYS -- En Route Equipment SystemsESF -- Extended Superframe FormatETA -- Estimated Time of ArrivalETE -- Estimated Time En RouteETG -- Enhanced Target GeneratorETMS -- Enhanced Traffic Management SystemETN -- Electronic Telecommunications NetworkEVAS -- Enhanced Vortex Advisory SystemEVCS -- Emergency Voice Communications SystemF topFAA -- Federal Aviation AdministrationF&E -- Facility and EquipmentFAAAC -- FAA Aeronautical CenterFAACIS -- FAA Communications Information SystemFAATC -- FAA Technical CenterFAC -- FacilityFAF -- Final Approach FixFAP -- Final Approach PointFAPM -- FTS2000 Associate Program ManagerFAR -- Federal Aviation RegulationFAATSAT -- FAA Telecommunications SatelliteFAST -- Final Approach Spacing ToolFAX -- Facsimile EquipmentFBO -- Fixed Base OperatorFBS -- Fall Back SwitchFCC -- Federal Communications CommissionFCLT -- Freeze Calculated Landing TimeFCOM -- FSS Radio Voice CommunicationsFCPU -- Facility Central Processing UnitFDAT -- Flight Data Entry and Printout (FDEP) and Flight Data Service FDE -- Flight Data EntryFDEP -- Flight Data Entry and PrintoutFDIO -- Flight Data Input/OutputFDIOC -- Flight Data Input/Output CenterFDIOR -- Flight Data Input/Output RemoteFDM -- Frequency Division MultiplexingFDP -- Flight Data ProcessingFED -- FederalFEIS -- Final Environmental Impact StatementFEP -- Front End ProcessorFFAC -- From FacilityFIFO -- Flight Inspection Field OfficeFIG -- Flight Inspection GroupFINO -- Flight Inspection National Field OfficeFIPS -- Federal Information Publication StandardFIR -- Flight Information RegionFIRE -- Fire StationFIRMR -- Federal Information Resource Management RegulationFL -- Flight LevelFLOWSIM -- Traffic Flow Planning SimulationFMA -- Final Monitor AidFMF -- Facility Master FileFMIS -- FTS2000 Management Information SystemFMS -- Flight management SystemFNMS -- FTS2000 Network Management SystemFOIA -- Freedom Of Information ActFONSI -- Finding of No Significant ImpactFP -- Flight PlanFRC -- Request Full Route ClearanceFSAS -- Flight Service Automation SystemFSDO -- Flight Standards District OfficeFSDPS -- Flight Service Data Processing SystemFSEP -- Facility/Service/Equipment ProfileFSP -- Flight Strip PrinterFSPD -- Freeze Speed ParameterFSS -- Flight Service StationFSSA -- Flight Service Station Automated ServiceFSTS -- Federal Secure Telephone ServiceFSYS -- Flight Service Station Equipment SystemsFTS -- Federal Telecommunications SystemFTS2000 -- Federal Telecommunications System 2000FUS -- Functional Units or SystemsFWCS -- Flight Watch Control StationG topGA -- General AviationGAA -- General Aviation ActivityGAAA -- General Aviation Activity and AvionicsGADO -- General Aviation District OfficeGCA -- Ground Control ApproachGIS -- Geographic Information SystemGNAS -- General National Airspace SystemGNSS -- Global Navigation Satellite SystemGOES -- Geostationary Operational Environmental SatelliteGOESF -- GOES Feed PointGOEST -- GOES Terminal EquipmentGPRA -- Government Performance Results ActGPS -- Global Positioning SatelliteGPWS -- Ground Proximity Warning SystemGRADE -- Graphical Airspace Design EnvironmentGS -- Glide Slope IndicatorGSA -- General Services AdministrationGSE -- Ground Support EquipmentH topH -- Non-- Directional Radio Homing Beacon (NDB)HAA -- Height Above AirportHAL -- Height Above LandingHARS -- High Altitude Route SystemHAT -- Height Above TouchdownHAZMAT -- Hazardous MaterialsHCAP -- High Capacity CarriersHLDC -- High Level Data Link ControlHDME -- NDB with Distance Measuring EquipmentHDQ -- FAA HeadquartersHELI -- HeliportHF -- High FrequencyHH -- NDB, 2kw or MoreHI-- EFAS -- High Altitude EFASHOV -- High Occupancy VehicleHSI -- Horizontal Situation IndicatorsHUD -- Housing and Urban DevelopmentHWAS -- Hazardous In-- Flight Weather AdvisoryHz -- HERTZI topIA -- Indirect AccessIAF -- Initial Approach FixI/AFSS -- International AFSSIAP -- Instrument Approach ProceduresIAPA -- Instrument Approach Procedures AutomationIBM -- International Business MachinesIBP -- International Boundary PointIBR -- Intermediate Bit RateICAO -- International Civil Aviation OrganizationICSS -- International Communications Switching SystemsIDAT -- Interfacility DataIF -- Intermediate FixIFCP -- Interfacility Communications ProcessorIFDS -- Interfacility Data SystemIFEA -- In-- Flight Emergency AssistanceIFO -- International Field OfficeIFR -- Instrument Flight RulesIFSS -- International Flight Service StationILS -- Instrument Landing SystemIM -- Inner MarkerIMC -- Instrument Meteorological ConditionsINM -- Integrated Noise ModelINS -- Inertial Navigation SystemIRMP -- Information Resources Management PlanISDN -- Integrated Services Digital NetworkISMLS -- Interim Standard Microwave Landing SystemITI -- Interactive Terminal InterfaceIVRS -- Interim Voice Response SystemIW -- Inside WiringJ top K topKbps -- Kilobits Per SecondKhz -- KilohertzKVDT -- Keyboard Video Display TerminalL topLAA -- Local Airport AdvisoryLAAS -- Low Altitude Alert SystemLABS -- Leased A B ServiceLABSC -- LABS GS-- 200 ComputerLABSR -- LABS Remote EquipmentLABSW -- LABS Switch SystemLAHSO -- Land and Hold Short OperationLAN -- Local Area NetworkLATA -- Local Access and Transport AreaLAWRS -- Limited Aviation Weather Reporting SystemLCF -- Local Control FacilityLCN -- Local Communications NetworkLDA -- Localizer Directional AidLDA -- Landing Directional AidLDIN -- Lead-- in LightsLEC -- Local Exchange CarrierLF -- Low FrequencyLINCS -- Leased Interfacility NAS Communications SystemLIS -- Logistics and Inventory SystemLLWAS -- Low Level Wind Shear Alert SystemLM/MS -- Low/Medium FrequencyLMM -- Locator Middle MarkerLMS -- LORAN Monitor SiteLOC -- LocalizerLOCID -- Location IdentifierLOI -- Letter of IntentLOM -- Compass Locator at Outer MarkerLORAN -- Long Range Aid to NavigationLPV -- Lateral Precision Performance with Vertical GuidanceLRCO -- Limited Remote Communications OutletLRNAV -- Long Range NavigationLRR -- Long Range RadarM topMAA -- Maximum Authorized AltitudeMALS -- Medium Intensity Approach Lighting SystemMALSF -- MALS with Sequenced FlashersMALSR -- MALS with Runway Alignment Indicator LightsMAP -- Maintenance Automation ProgramMAP -- Military Airport ProgramMAP -- Missed Approach PointMAP -- Modified Access PricingMbps -- Megabits Per SecondMCA -- Minimum Crossing AltitudeMCAS -- Marine Corps Air StationMCC -- Maintenance Control CenterMCL -- Middle Compass LocaterMCS -- Maintenance and Control SystemMDA -- Minimum Descent AltitudeMDT -- Maintenance Data TerminalMEA -- Minimum En Route AltitudeMETI -- Meteorological InformationMF -- Middle FrequencyMFJ -- Modified Final JudgmentMFT -- Meter Fix Crossing Time/Slot TimeMHA -- Minimum Holding AltitudeMhg -- MegHERTZMIA -- Minimum IFR AltitudesMIDO -- Manufacturing Inspection District OfficeMIS -- Meteorological Impact StatementMISC -- MiscellaneousMISO -- Manufacturing Inspection Satellite OfficeMIT -- Miles In TrailMITRE -- Mitre CorporationMLS -- Microwave Landing SystemMM -- Middle MarkerMMC -- Maintenance Monitoring ConsoleMMS -- Maintenance Monitoring SystemMNPS -- Minimum Navigation Performance SpecificationMNPSA -- Minimum Navigation Performance Specifications Airspace MOA -- Memorandum of AgreementMOA -- Military Operations AreaMOCA -- Minimum Obstruction Clearance AltitudeMODE C -- Altitude-- Encoded Beacon ReplyMODE C -- Altitude Reporting Mode of Secondary RadarMODE S -- Mode Select Beacon SystemMOU -- Memorandum of UnderstandingMPO -- Metropolitan Planning OrganizationMPS -- Maintenance Processor Subsystem (OR) Master Plan Supplement MRA -- Minimum Reception AltitudeMRC -- Monthly Recurring ChargeMSA -- Minimum Safe AltitudeMSAW -- Minimum Safe Altitude WarningMSL -- Mean Sea LevelMSN -- Message Switching NetworkMTCS -- Modular Terminal Communications SystemMTI -- Moving Target IndicatorMUX -- MultiplexorMVA -- Minimum Vectoring AltitudeMVFR -- Marginal Visual Flight RulesN topNAAQS -- National Ambient Air Quality StandardsNADA -- NADIN ConcentratorNADIN -- National Airspace Data Interchange NetworkNADSW -- NADIN SwitchesNAILS -- National Airspace Integrated Logistics SupportNAMS -- NADIN IANAPRS -- National Airspace Performance Reporting SystemNAS -- National Airspace System or Naval Air StationNASDC -- National Aviation Safety DataNASP -- National Airspace System PlanNASPAC -- National Airspace System Performance Analysis Capability NATCO -- National Communications Switching CenterNAVAID -- Navigation AidNAVMN -- Navigation Monitor and ControlNAWAU -- National Aviation Weather Advisory UnitNAWPF -- National Aviation Weather Processing FacilityNCAR -- National Center for Atmospheric Research; Boulder, CONCF -- National Control FacilityNCIU -- NEXRAD Communications Interface UnitNCP -- Noise Compatibility ProgramNCS -- National Communications SystemNDB -- Non-- Directional Radio Homing BeaconNDNB -- NADIN IINEM -- Noise Exposure MapNEPA -- National Environmental Policy ActNEXRAD -- Next Generation Weather RadarNFAX -- National Facsimile ServiceNFDC -- National Flight Data CenterNFIS -- NAS Facilities Information SystemNI -- Network InterfaceNICS -- National Interfacility Communications SystemNPE -- Non-primary Airport EntitlementNPIAS -- National Plan of Integrated Airport SystemsNM -- Nautical MileNMAC -- Near Mid Air CollisionNMC -- National Meteorological CenterNMCE -- Network Monitoring and Control EquipmentNMCS -- Network Monitoring and Control SystemNOAA -- National Oceanic and Atmospheric AdministrationNOC -- Notice Of CompletionNOTAM -- Notice to AirmenNPDES -- National Pollutant Discharge Elimination SystemNPIAS -- National Plan of Integrated Airport SystemsNRC -- Non-- Recurring ChargeNRCS -- National Radio Communications SystemsNSAP -- National Service Assurance PlanNSRCATN -- National Strategy to Reduce Congestion on America's Transportation NetworkNSSFC -- National Severe Storms Forecast CenterNSSL -- National Severe Storms Laboratory; Norman, OKNTAP -- Notices To Airmen PublicationNTP -- National Transportation PolicyNTSB -- National Transportation Safety BoardNTZ -- No Transgression ZoneNWS -- National Weather ServiceNWSR -- NWS Weather Excluding NXRDNSWRH -- NWS Regional HeadquartersNXRD -- Advanced Weather Radar SystemO topOAG -- Official Airline GuideOALT -- Operational Acceptable Level of TrafficOAW -- Off-- airway Weather StationODAL -- Omnidirectional Approach Lighting SystemODAPS -- Oceanic Display and Processing StationOEP -- Operational Evolution Plan / PartnershipOFA -- Object Free AreaOFDPS -- Offshore Flight Data Processing SystemOFT -- Outer Fix TimeOFZ -- Obstacle Free ZoneOM -- Outer MarkerOMB -- Office of Management and BudgetONER -- Oceanic Navigational Error ReportOPLT -- Operational Acceptable Level of TrafficOPSW -- Operational SwitchOPX -- Off Premises ExchangeORD -- Operational Readiness DemonstrationOTR -- Oceanic Transition RouteOTS -- Organized Track SystemP topPABX -- Private Automated Branch ExchangePAD -- Packet Assembler/DisassemblerPAM -- Peripheral Adapter ModulePAPI -- Precision Approach Path IndicatorPAR -- Precision Approach RadarPAR -- Preferential Arrival RoutePATWAS -- Pilots Automatic Telephone Weather Answering ServicePBCT -- Proposed Boundary Crossing TimePBRF -- Pilot BriefingPBX -- Private Branch ExchangePCA -- Positive Control AirspacePCM -- Pulse Code ModulationPDAR -- Preferential Arrival And Departure RoutePDC -- Pre-- Departure ClearancePDC -- Program Designator CodePDR -- Preferential Departure RoutePDN -- Public Data NetworkPFC -- Passenger Facility ChargePGP -- Planning Grant ProgramPIC -- Principal Interexchange CarrierPIDP -- Programmable Indicator Data ProcessorPIREP -- Pilot Weather ReportPMS -- Program Management SystemPOLIC -- Police StationPOP -- Point Of PresencePOT -- Point Of TerminationPPIMS -- Personal Property Information Management SystemPR -- Primary Commercial Service AirportPRI -- Primary Rate InterfacePRM -- Precision Runway MonitorPSDN -- Public Switched Data NetworkPSN -- Packet Switched NetworkPSS -- Packet Switched ServicePSTN -- Public Switched Telephone NetworkPTC -- Presumed-to-ConformPUB -- PublicationPUP -- Principal User ProcessorPVC -- Permanent Virtual CircuitPVD -- Plan View DisplayQ topR topRAIL -- Runway Alignment Indicator LightsRAPCO -- Radar Approach Control (USAF)RAPCON -- Radar Approach Control (FAA)RATCC -- Radar Air Traffic Control CenterRATCF -- Radar Air Traffic Control Facility (USN)RBC -- Rotating Beam CeilometerRBDPE -- Radar Beacon Data Processing Equipment RBSS -- Radar Bomb Scoring SquadronRCAG -- Remote Communications Air/GroundRCC -- Rescue Coordination CenterRCF -- Remote Communication FacilityRCCC -- Regional Communications Control Centers RCIU -- Remote Control Interface UnitRCL -- Radio Communications LinkRCLR -- RCL RepeaterRCLT -- RCL TerminalRCO -- Remote Communications OutletRCU -- Remote Control UnitRDAT -- Digitized Radar DataRDP -- Radar Data ProcessingRDSIM -- Runway Delay Simulation ModelREIL -- Runway End Identification LightsRF -- Radio FrequencyRL -- General Aviation Reliever AirportRMCC -- Remote Monitor Control CenterRMCF -- Remote Monitor Control FacilityRML -- Radio Microwave LinkRMLR -- RML RepeaterRMLT -- RML TerminalRMM -- Remote Maintenance MonitoringRMMS -- Remote Maintenance Monitoring System RMS -- Remote Monitoring SubsystemRMSC -- Remote Monitoring Subsystem Concentrator RNAV -- Area NavigationRNP -- Required Navigation PerformanceROD -- Record of DecisionROSA -- Report of Service ActivityROT -- Runway Occupancy TimeRP -- Restoration PriorityRPC -- Restoration Priority CodeRPG -- Radar Processing GroupRPZ -- Runway Protection ZoneRRH -- Remote Reading HygrothermometerRRHS -- Remote Reading HydrometerRRWDS -- Remote Radar Weather DisplayRRWSS -- RWDS Sensor SiteRSA -- Runway Safety AreaRSAT -- Runway Safety Action TeamRSS -- Remote Speaking SystemRT -- Remote Transmitter。