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