|
Definition
|
Contraction
|
Usage
|
|
U.S. Air Force
|
USAF
|
GEN
|
|
U.S. Army
|
USA
|
GEN
|
|
U.S. Army Aviation Flight
Information
|
USAFIB
|
GEN
|
|
U.S. Coast Guard
|
USCG
|
GEN
|
|
U.S. Marine Corps
|
USMC
|
GEN
|
|
U.S. Navy
|
USN
|
GEN
|
|
ultra high frequency
|
UHF
|
ICAO
|
|
ultra high frequency direction
finding station
|
UDF
|
ICAO
|
|
Unable
|
UN
|
GEN
|
|
Unable
|
UNA
|
ICAO
|
|
unable higher altitude
|
UHA
|
ATC
|
|
unable higher due opposite direction
traffic
|
UHDODT
|
ATC
|
|
unable higher due same direction
traffic
|
UHDSDT
|
ATC
|
|
unable higher due traffic
|
UHDT
|
ICAO
|
|
unable higher due traffic
|
UHDT
|
ICAO
|
|
unable lower due traffic
|
ULDT
|
ATC
|
|
unable to approve
|
UNAP
|
ICAO
|
|
unable to approve
|
UNAPV
|
GEN
|
|
unable to approve altitude requested
|
UNAR
|
ATC
|
|
unable to approve arrival for the
time specified
|
UA
|
ATC
|
|
unable to approve departure for the
time specified
|
UD
|
ATC
|
|
unable to approve route requested
|
UNRR
|
ATC
|
|
unable to contact company radio
|
UNCC
|
ATC
|
|
unable to establish contact
|
UNTC
|
ATC
|
|
unable to finish
|
INSUF
|
GEN
|
|
unable to maintain
|
UM
|
ATC
|
|
unable to monitor
|
UNMON
|
GEN
|
|
unable to transmit
|
NIL
|
GEN
|
|
Unattended
|
UNATNDD
|
GEN
|
|
Unavailable
|
UNAVBL
|
GEN
|
|
uncertainty phase code (alerting
service)
|
INCERFA
|
ATC
|
|
Undelivered
|
UNDLD
|
GEN
|
|
Unheard
|
UNHRD
|
GEN
|
|
Unidentified
|
UNID
|
GEN
|
|
unidentified flying object
|
UFO
|
GEN
|
|
United States Naval Observatory
|
USNO
|
ATC
|
|
United States NOTAM Office
|
USNOF
|
GEN
|
|
United States NOTAM System
|
USNS
|
GEN
|
|
unknown
|
UNKN
|
GEN
|
|
unknown precipitation
|
UP
|
METAR
|
|
unlighted
|
UNLGTD
|
GEN
|
|
unlimited
|
UNL
|
ICAO
|
|
unmonitored
|
UNMON
|
ATC
|
|
unnecessary
|
UNEC
|
GEN
|
|
unofficial
|
UNOFFL
|
GEN
|
|
unquote
|
UQOT
|
GEN
|
|
unreadable
|
UNRDBL
|
GEN
|
|
unreliable
|
UNREL
|
ICAO
|
|
unreliable
|
UNRELBL
|
GEN
|
|
unrestricted
|
UNRSTD
|
GEN
|
|
unsatisfactory
|
UNSATFY
|
GEN
|
|
unscheduled
|
UNSKED
|
GEN
|
|
unseasonable
|
UNSBL
|
NWS
|
|
unserviceable
|
U/S
|
ICAO
|
|
unsettle
|
UNSTL
|
NWS
|
|
unstable
|
UNSTBL
|
NWS
|
|
unsteady
|
UNSTDY
|
NWS
|
|
until
|
TIL
|
GEN
|
|
until advised by
|
UAB
|
ATC
|
|
until advised by the tower
|
UAT
|
ATC
|
|
until cleared down
|
UCDWN
|
ATC
|
|
until cleared to land by the tower
|
UCLT
|
ATC
|
|
until further advised
|
UFA
|
GEN
|
|
until further notice
|
UFN
|
GEN
|
|
until past
|
TIP
|
ATC
|
|
untra long range
|
ULR
|
ICAO
|
|
unusable
|
UNUSBL
|
GEN
|
|
up and down drafts
|
UDDF
|
NWS
|
|
up drafts
|
UPDFTS
|
NWS
|
|
update
|
UPDT
|
NWS
|
|
upper
|
UPR
|
NWS
|
|
upper air route
|
UAR
|
ICAO
|
|
upper area control center
|
UAC
|
ICAO
|
|
upper atmosphere geophysics
|
UAG
|
NWS
|
|
upper control area
|
UTA
|
ICAO
|
|
upper flight information region
|
UIR
|
ICAO
|
|
upper information center
|
UIC
|
ICAO
|
|
upper winds
|
UWNDS
|
NWS
|
|
upper winds obs. (by radio methods)
|
RAWIN
|
NWS
|
|
upslope
|
UPSLP
|
NWS
|
|
upstream
|
UPSTRM
|
NWS
|
|
upward vertical velocity
|
UVV
|
NWS
|
|
upwind
|
UW
|
ATC
|
|
urgent
|
URG
|
GEN
|
|
urgent PIREP
|
UUA
|
ATC
|
|
urgent special observation (weather
reports only)
|
USP
|
NWS
|
|
usable
|
USBL
|
GEN
|
|
User Equivalent Range Error
|
UERE
|
ATC
|
