aviation acronyms and abbreviations > U

U: Uniform 
U/C: Under Carriage 
U/C: Undercarriage 
U/D: Upper Deck 
U/FULL: Under Full 
U/I: Unidentified 
U/J: Universal Joint 
u/t: under training 
UA: United Airlines 
UART: Universal Asynchronous Receiver/Transmitter 
UAS: University Air Squadron 
UC: Upgrade Credit 
UD: Upper Deck 
UDC: Upper Deck Cargo 
UDL: Unit Detail Listing 
UE: User Equipment 
UED: Universal Equipment Depot 
UER: Unscheduled Engine Removal 
UERE: User Equivalent Range Error 
UF: Under Frequency 
UF: Uplink Format 
UFD: Unit Fault Data 
UG: UpGrade 
UHF: Ultra High Frequency 
UKADGE: UK Air Defence Ground Environment 
UKADR: UK Air Defence Region 
UKRAOC: UK Regional Air Operations Centre 
ULB: Underwater Locator Beacon 
ULD: Unit Loading Device 
ULH: Ultra Long Haul 
UM: Unaccompanied Minor 
UMVF: Unmanned Vertical Flight 
UNA: Unavailable 
unbal: unbalance 
UNCPLG: Uncoupling 
UNCRCTD: Uncorrected 
UND: Under 
UNIV: Universal 
UNLK: unlock 
UNLKD: Unlocked