PNF  Pilot.Not.Flying 
PNR  Point.of.No.Return 
POA  Plain Old ACARS 
POC  Proof Of Concept. A Demonstration, in a full operational.environment,.of.the.proposed. concept,.system,.facilities,.weather.conditions,. crew.complement,.related.aircraft.systems.and. any.other.relevant.parameters.necessary.to.show. concept.validity..Acceptable.performance,.system. reliability,.repeatability,.and.typical.pilot.response. to.failures.must.be.successfully.demonstrated.. The demonstration itself is not a certification 
program. 
POI  Principal Operations Inspector 
POP  Point.of.Presence 
POR  Pacific Ocean Region 
POS  Position 
POSINIT  Position.Initialization 
POSIX  Portable Operating System Interface 
POSREF  Position.Reference 
POT  Potentiometer 
POST  Power-On Self-Test 
POTS  Plain Old Telephone System/Service 
P/PAP  Product/Process.Assurance.Plan 
PPC  Power.PC 
PPDU  Physical.Layer.Protocol.Data.Unit 
PPI  Planned.Position.Indicator..A.type.of.radar.display. which.shows.aircraft.positions.and.airways.chart. on.the.same.display. 
PPL  Processor-to-Processor.Link 
ppm  pages.per.minute 
PPM  (.1.).Pulse.Position.Modulation.. (.2.).Parts.Per.Million 
PPOS  Present.Position 
PPP  Point-to-Point.Protocol 

PPS

PR PRAIM
PRAM PRELIM PRESS Pressure
Altitude
PREV
Preventive Advisory

PRF PRI
Primary Means of Navigation
PRM
PRN PRNAV PROC PROF PROG PROM
(.1.).Packets.Per.Second. (.2.).Precise.Positioning.Service. (.3.).Pulse.Per.Second
Problem.Report
Predictive.Receiver.Autonomous.Integrity. Monitoring Prerecorded.Announcement.Machine Preliminary.Data Pressure The.altitude.measured.above.standard.pressure.
level..Based.on.the.relationship.of.pressure.and. altitude.with.respect.to.a.standard.atmosphere.
Previous A.resolution.advisory.that.instructs.the.pilot.to. avoid.certain.deviations.from.current.vertical.rate.. (TCAS)
Pulse Repetition Frequency
(.1.).Primary.. (.2.).Primary.Rate.Interface
A means of navigation which satisfies the
necessary.levels.of.accuracy.and.integrity.for.a. particular.area,.route,.procedure.or.operation.. The.failure.of.a.“Primary.Means”.of.navigation.