TABLE OF CONTENTS | a | - Large Semi-major Axis of Elliptical Orbit |
| A | - Apogee |
| A | - Azimuth Angle |
| A/D | - Analog to digital signal conversion |
| AAC | - Aeronautical Administrative Communications |
| AAC-AOC | - Airline Administrative and Airline Operational Control |
| AAIC | - Accounting authority for satellite traffic invoicing |
| ABR | - Available Bit Rate |
| ACARS | - Aircraft Communications Addressing and Reporting System |
| ACARS | - Aircraft Communication and Reporting System |
| ACARS | - ARINC Communication and Reporting System |
| ACC | - Aeronautical Control Centre |
| ACK | - Acknowledgement |
| ACO | - Aeronautical Communications Organization |
| ACR | - Allowed Cell Rate |
| ACS | - Attitude Control System |
| ACS | - Assembly and Command Ship |
| ACSE | - Antenna Control and Signaling Equipment of LES |
| ACSSB | - Amplitude Companded SSB |
| ACU | - Above Cockpit Unit (Antenna Equipment of AES) |
| ACU | - Antenna Control Unit |
| ADE | - Above Deck Equipment (Antenna Equipment of SES) |
| ADM | - Adaptive Delta Modulation |
| ADPCM | - Adaptive Differential PCM |
| ADPS | - Aeronautical Data Processing System |
| ADREP | - Accident/Incident Data Reporting |
| ADSL | - Asymmetrical Digital Subscriber Line |
| ADSS | - Automatic Dependent Surveillance System |
| AEEC | - Airline Electronic Engineering Committee |
| AEIS | - Aeronautical Enroute Information Service |
| AES | - Aircraft (Aeronautical) Earth Station |
| AFC | - Automatic Frequency Control |
| AFIS | - Airborne Flight Information Service |
| AFTAX | - Aeronautical Fixed Telecommunication Automatic Exchange |
| AFTN | - Aeronautical Fixed Telecommunication Network |
| AGC | - Automatic Gain Control |
| AHD | - Above Haul Device (Antenna Equipment of VES) |
| AHNIS | - Aeronautical Highlights and Navigation Information Services |
| AIDC | - ATS Interfacility Data Communications |
| AIES | - Aeronautical Information Enroute Service |
| AIRCOM | - Aeronautical Communications |
| AKM |
