Off-Block Time The time that the aircraft leaves the gate. OFP Operational Flight Program
OID  Outline Installation Drawing 
OIU  Orientation/Introduction Unit 
OLAN  Onboard Local Area Network 
OM  Outer Marker 
OMEGA  A navigation system that uses two high-powered transmitter ground stations to broadcast a continuous wave signal. The receiver measures the range differ-ence between the two stations to determine position. 
Omnibearing  The bearing indicated by a navigational receiver on transmissions from an omnidirectional radio range (VOR). 
OMS  (1) Onboard Maintenance System (2) Order Management System 
OOOI  OUT-OFF-ON-IN. An OOOI event is recorded as part of the ACARS operation. The OUT event is recorded when the aircraft is clear of the gate and ready to taxi. The OFF event occurs when the aircraft has lift-
ed off the runway. The ON event occurs when the aircraft has landed. The IN event occurs when the air-
craft has taxied to the ramp area. 

On-Block Time The time that the aircraft arrives at the gate.
OPAS  Overhead Panel ARINC 629 System 
OPBC  Overhead Panel Bus Controller 
OPR  Once Per Revolution 
OPS  Operations Per Second 
OPU  Overspeed Protection Unit 
OR  Operational Requirements 
OSC  Order Status Report 
OSI  (1) Open Systems Interconnection 
(2) Open System Interface 
OTH  Over The Horizon 
OTS  Organized Track System 
OVRD  Override 

oxy  Oxygen 
P 
PA  (1) Passenger Address 
(2) Power Amplifier 
PAC  Path Attenuation Compensation 
PA/CI  Passenger Address/Cabin Interphone 
PACIS  Passenger Address and Communication Interphone 
System 
Paired  DME channels are paired with a VORTAC or ILS fre 
Channels  quency and are automatically selected when the VOR 
TAC or ILS frequency is selected.Most navigation con 
trols have this feature.