|
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
|
|
Unmanned
Aerial System
|
UAS
|
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
|