User Agent Server 
Unmanned Aircraft Systems 
Unmanned Aircraft System 
User Agents 
Unmanned Aerial Systems 
Unmanned Aerial System 
User Application Software 
Ukrainian Academy of Sciences 
UnAvailable Seconds 
Unified Antenna Structure 
Uniform Access Solution 
Uniform Accounting System 
University Air Squadron 
University of Agricultural Sciences 
University of Alaska Southeast 
Unmanned Air Systems 
upstream activation sequence 
Urban Areas 
Urgent Action Survey 
User Authorization Status 
Ulster Archeological Society 
ultrasonically activated scalpel 
Ultrasonically activated shears 
umbilical arteries 
Unassigned 
Unavailable Second 
Unexplained Anomalies 
Uniform Access Services 
Union of African States 
Unit Approval System