| Abbreviation | Definition |
|---|---|
| A/C | Air Conditioning |
| A/C | Associate Contractor |
| A/D | Analog-to-Digital |
| A/E | Activity Elements |
| A/E | Architectural and Engineering |
| A/F | Air-to-Fuel Ratio |
| A/FM | Air/Firing Mechanism |
| A/G | Air to Ground |
| A/L | AirLock |
| A/L | Approach and Landing |
| A/L | AutoLand |
| AA | Antenna Assembly |
| AA | Astronomical Applications |
| AAA | Avionics Air Assembly |
| AAC | Aft Access Closure |
| AACB | Aeronautics and Astronautics Coordinating Board |
| AAD | Attitude Anomaly Detector |
| AAEU | Aquatic Animal Experiment Unit |
| AAFE | AeroAssist Flight Experiment |
| AAFM | Acoustic Atomic Force Microscopy |