Airworthiness Directives 
Aero Design Std 
Astrophysics Data System 
Automatic Dependent Surveillance 
Advanced Deployable System 
Active Denial System 
Airspace Deconfliction System 
Application Development System 
Advanced Design System 
Advanced Digital System 
Automated Deployment Services 
Audio Distribution System 
Auxilliary Discriminating Sensor 
Advanced Distributed Simulation 
Automatic Dependence Surveillance 
Auxilary Data System 
Alternative Depreciation System 
Automated Data System 
Automated Directives System 
Accelerator Driven System 
ACCURATELY DEFINED SYSTEM 
Activity Data Sheet 
Advanced Display System 
Advanced Dressing Station 
Aerospace Data Systems 
Aitken Double Stars 
Alternate Data Streams 
Attitude Determination System 
Attitude Display System 
automatic data system