|
Definition
|
Contraction
|
Usage
|
|
Obliterate
|
OBL
|
GEN
|
|
Obscure
|
OBSC
|
NWS
|
|
obscured
sky condition
|
X
|
NWS
|
|
Observation
|
OBS
|
NWS
|
|
Obstacle
|
OBST
|
ICAO
|
|
obstacle
assessment surface
|
OAS
|
ICAO
|
|
obstacle
clearance altitude
|
OCA
|
ICAO
|
|
obstacle
clearance height
|
OCH
|
ICAO
|
|
obstacle
clearance limit
|
OCL
|
ICAO
|
|
obstacle
clearance surface
|
OCS
|
ICAO
|
|
Obstacle
free zone
|
OFZ
|
ICAO
|
|
Obstruct
|
OBST
|
GEN
|
|
Obstruction
|
OBSTN
|
GEN
|
|
obstruction
chart
|
OC
|
GEN
|
|
Occasional
|
OCNL
|
GEN
|
|
Occlude
|
OCLD
|
NWS
|
|
occluded
frontal passage
|
OFP
|
NWS
|
|
Occlusion
|
OCLN
|
NWS
|
|
occluded
front
|
OCFNT
|
NWS
|
|
Occur
|
OCR
|
GEN
|
|
ocean
station vessel
|
OSV
|
NWS
|
|
oceanic
air route tracking system
|
OARTS
|
GEN
|
|
oceanic
area control
|
OAC
|
GEN
|
|
oceanic
ATC
|
OCAC
|
GEN
|
|
oceanic
control area
|
OCA
|
ICAO
|
|
Oceanic
Display and Planning System
|
ODAPS
|
ATC
|
|
oceanic
navigational error report
|
ONER
|
ATC
|
|
off watch
|
OFW
|
GEN
|
|
Office
|
OFC
|
GEN
|
|
Official
|
OFFL
|
GEN
|
|
Official
Airline Guide
|
OAG
|
GEN
|
|
Offshore
|
OFSHR
|
NWS
|
|
omni
intersection
|
OINT
|
GEN
|
|
omnidirectional
approach lighting system
|
ODALS
|
GEN
|
|
on and off
instruments
|
OAOI
|
ATC
|
|
on board
|
OB
|
GEN
|
|
on course
|
OC
|
ATC
|
|
on file
|
O/F
|
GEN
|
|
on ground
|
OG
|
ATC
|
|
on
instruments
|
OI
|
ATC
|
|
On line
data interchange
|
OLDI
|
ICAO
|
|
on request
|
O/R
|
GEN
|
|
on shore
|
ONSHR
|
NWS
|
|
on time
|
OT
|
ATC
|
|
on top
|
OTP
|
ATC
|
|
on top and
smooth
|
OTAS
|
NWS
|
|
on watch
|
ONW
|
GEN
|
|
one way
|
OW
|
GEN
|
|
Ontario
|
ONT
|
NWS
|
|
onthejob
training
|
OJT
|
GEN
|
|
opaque,
white type of ice formation
|
OPA
|
ICAO
|
|
open
|
OPN
|
ICAO
|
|
operate
|
OPER
|
GEN
|
|
operate,
operator, operational
|
OPR
|
ICAO
|
|
operating
normally
|
OK
|
GEN
|
|
operation
|
OPN
|
GEN
|
|
operation
and regulation
|
OANDR
|
GEN
|
|
operational
control
|
OPC
|
ICAO
|
|
operational
information system
|
OIS
|
ATC
|
|
operational
meteorological (information)
|
OPMET
|
ICAO
|
|
operations
|
OPS
|
ICAO
|
|
operations
network
|
OPSNET
|
ATC
|
|
operations
normal
|
OPNML
|
GEN
|
|
opposite
direction traffic
|
OPDT
|
GEN
|
|
optical
landing system
|
OLS
|
ATC
|
|
optimum
working frequency
|
OWF
|
GEN
|
|
order,
indication of
|
ORD
|
ICAO
|
|
organized
track system
|
OTS
|
GEN
|
|
original
|
ORIG
|
GEN
|
|
original
flight plan
|
OFP
|
GEN
|
|
Originate
|
OGN
|
ICAO
|
|
orographic
|
ORGPHC
|
NWS
|
|
other
|
OTR
|
GEN
|
|
otherwise
|
OTRW
|
GEN
|
|
our
message
|
OMSG
|
GEN
|
|
out for
maintenance
|
OFM
|
GEN
|
|
out of
control area
|
OCTLA
|
ATC
|
|
out of
controlled airspace
|
OCAS
|
ATC
|
|
out of
service
|
OTS
|
GEN
|
|
out of
tolerance
|
OOT
|
GEN
|
|
outbound
|
OBND
|
ATC
|
|
outbound
|
OUBD
|
ICAO
|
|
outer fix
time
|
OFXT
|
ATC
|
|
outer
locator
|
LO
|
ICAO
|
|
outer
marker
|
OM
|
GEN
|
|
outlook
|
OTLK
|
NWS
|
|
outside
air temperature
|
OAT
|
GEN
|
|
over
|
OVR
|
GEN
|
|
over
mountains
|
OMTNS
|
NWS
|
|
over range
station
|
ORS
|
ATC
|
|
overcast
|
OVC
|
NWS
|
|
overdue
|
OVD
|
GEN
|
|
overflight
traffic
|
OTFC
|
GEN
|
|
overhead
|
OHD
|
ICAO
|
|
overhead
|
OVHD
|
GEN
|
|
overhead
approach
|
OA
|
ATC
|
|
overlay
|
OVLA
|
GEN
|
|
overnight
|
OVNGT
|
GEN
|
|
overrun
|
OVRN
|
GEN
|
|
overrun
lights
|
ORL
|
GEN
|
|
overseas
|
OVSEA
|
GEN
|
|
overseas
flight assistance service
|
OFAS
|
GEN
|
|
overtake
|
OVTK
|
GEN
|
|
overtime
|
O/T
|
GEN
|
|
oxygen
|
OXY
|
GEN
|