## U 

UAS —unmanned aircraft systems UFN —until further notice UHF —ultra high frequency UNAVBL —unavailable UNLGTD —unlighted UNMKD —unmarked UNMNT —unmonitored UNREL —unreliable UNUSBL —unusable URA —Uniform Relocation Assistance and Real Property Acquisition Policies Act of 1970 USAF —United States Air Force USC —United States Code USOC —Uniform Service Order Code 

## V 

V/PD —Vehicle/pedestrian deviation VALE —voluntary airport low emission VASI —visual approach slope indicator VDME —VOR with distance measuring equipment VDP —visual descent point VF —voice frequency VFR —visual flight rules VGSI —visual glide slope indicator VHF —very high frequency VIA —by way of VICE —instead/versus VIS —visibility VLF —very low frequency VMC —visual meteorological conditions VNAV —visual navigational aids VNTSC —Volpe National Transportation System Center VOL —volume VON —virtual on-net VOR —VHF omnidirectional range VOR/DME —VHF omnidirectional range/distance measuring equipment VORTAC —VOR and TACAN (collocated) VOT —VOR Test Facility VP/D —vehicle/pedestrian deviation VRS —voice recording system VSCS —voice switching and control system VTA —vertex time of arrival VTAC —VOR and TACAN (collocated) VTOL —vertical takeoff and landing VTS —voice telecommunications system 

## W 

W —west WAAS —Wide Area Augmentation System WAN —wide area network WB —westbound WC —work center WCP —Weather Communications Processor WECO —Western Electric Company WED —Wednesday WEF —with effect from; effective from WESCOM —Western Electric Satellite Communications WI —within WIE —with immediate effect, or effective immediately WKDAYS —Monday through Friday WKEND —Saturday and Sunday WMSC —Weather Message Switching Center WMSCR —Weather Message Switching Center Replacement WND —wind WPT —waypoint WSCMO —Weather Service Contract Meteorological Observatory WSFO —Weather Service Forecast Office WSMO —Weather Service Meteorological Observatory WSO —Weather Service Office WSR —wet snow on runway(s) WTHR —weather WTR —water on runway(s) WX —weather 

