(
 3 ) Airline Operational Control.

(
 4 ) Airport Obstruction Chart.

( 5 ) Airport Operational Communications AOCC Airline Operation Control Center AOD Audio.on.Demand AODC Age.of.Data,.Clock.(GPS.term) AODE Age.of.Data,.Ephemeris.(GPS.term)

AOG Aircraft.on.Ground AOHE Air/Oil Heat Exchanger AOM Aircraft Operating Manual AOP ( 1 ) Aeronautical OSI Profile .
( 2 ) Airline Operational Procedure AOPA Aircraft Owners and Pilots Association AOPG Aerodrome Operations Group AOR Atlantic Ocean Region AOR-E Atlantic Ocean Region-East AOR-W Atlantic Ocean Region-West A/P Autopilot..A.computer.commanded.system.for.
controlling.aircraft.control.surfaces. AP Airport.Location.(ACARS/AFERS) APA (.1.).Allied.Pilots.Association..
( 2 ) Autopilot Amplifier
APB Auxiliary.Power.Breaker APC (.1.).Autopilot.Computer.. (.2.).Aeronautical.Public.Correspondence..
(.3.).Aeronautical.Passenger.Communication API Application.Programming.Interface APM Aircraft.Personality.Module APMS Automated.Performance.Measurement.System APN ARINC.Packet.Network APP (.1.).Approach.Control..
(.2.).Autopilot.Panel App Application APPR Approach: That segment of flight having to do
with final descent and landing.
APR Actual.Performance.Reserve APRL ATN Profile Requirement List APS Autopilot.System APU Auxiliary.Power.Unit APUC Auxiliary.Power.Unit.Controller

AQF  Avionics Qualification Facility 
AQP  ( 1 ) Advanced Qualification Program. ( 2 ) Avionics Qualification Procedure 
A-QPSK  Aeronautical.Quadrature.Phase.Shift.Keying 
AQS  Advanced.Quality.System 
ARAC  Aviation.Rule.making.Advisory.Committee 
ARB  Arbitrary.Waveform.Generator 
ARF  Airline.Risk.Factor 
ARINC  Aeronautical.Radio,.INCorporated:.Corporation.in. which.the.U.S..scheduled.airlines.are.the.major. stockholders. 
ARINC  -XXX Digital database protocols defined by ARINC.committee. 
ARMC  Area.Regional.Maintenance.Center 
ARP  (.1.).Aeronautical.Recommended.Practice... (.2.).Air.Data.Reference.Panel.. (.3.).Airport.Reference.Point:.Point.in.space. based.on.a.particular.altitude,.waypoint.and/or. offset..The.FMS.makes.calculations.to.guide.the. aircraft.to.that.particular.point. 
ARPA  Advanced.Research.Projects.Agency 
ARPT  Airport 
ARR  Arrival 
ARS  Automated.Radar.Summary.chart...These.are. hourly.generated.charts.showing.location.and. intensity.of.radar.echoes. 
ARSR  Air.Route.Surveillance.Radar 
ART  Automatic.Reserve.Thrust 
ARTT  Adaptive Radar Threshold Techniques 
ARTCC  Air-Route Traffic Control Center. Approximately 20 centers cover the air traffic routes in the United.States.using.numerous.radars.and.radio. communication.sets.