AAE:  Above Aerodrome Elevation
A/FD: Airport/Facility Directory, a book updated very 54 days with detailed information about 
Airports within its coverage area. 
ABEAM: An aircraft is abeam a fix, point or object when that point is approximately 90 degrees to the right or left of the aircraft track. 
ABORT: To terminate a planned aircraft maneuver.
ACKNOWLEDGE: An expression used in radio communication meaning "let me know that you have received and understood the message"
A/C: Abbreviation for Aircraft.
ACC: Area Control Center.
ACFT: Another possible abbreviation for Aircraft
ACTIVE RUNWAY: Another expression for Runway in use.
ADF: Automatic Direction Finder, a radio system that senses and indicates the direction to an NDB 
ADVISE INTENTIONS: An expression used in radio communication meaning "tell me what you are planning to do"
AGL: Above Ground Level, the Height expressed in feet measured above Ground Level.
AIRCRAFT CALL SIGN: A group of alphanumeric characters used to identify an aircraft in air-ground communications.
AIP: Aeronautical Information Publication
AIRMET: A weather advisory concerning hazardous weather conditions such as icing, turbulence, low ceilings, etc. 
AIRWAY: A corridor between radio navaids. 
ALT: Abbreviation for Altitude, the vertical distance of a level or an object considered a point, measured from Mean Sea Level
ALTIMETER SETTING: The barometric pressure reading used to adjust the pressure altimeter for variations in atmospheric pressure or to the standard setting of 1013 hectoPascal. (Hpa)
AMSL: Altitude Above Mean Sea Level
APPROACH: An ATC facility that provides control for aircraft arriving and departing an airport. 
ARC: A curved ground track of an aircraft flying at a constant distance from a navaid referenced by distance measuring equipment.
ARTCC: Air Route Traffic Control Center, or just "Center", the en-route air traffic control facility. 
ATC: Air Traffic Control, a control facility at airports and other controlled airspace. 
ATIS: Automatic Terminal Information Service, a recorded message with information about an airports active runways, weather conditions, etc.



BACKTRACK: To taxi on the active runway in the direction opposite to landing aircraft, usually to position the aircraft for takeoff at an airport with no taxiways. 
BASE: The part of the landing traffic pattern where the plane flies at a 90 degree angle to that of the landing runway. 
BEARING: The horizontal direction to or from any point, usually measured clockwise from true north. Magnetic north or a reference point through 360'.
BRAKING ACTION REPORT: A report of conditions at the airport movement area providing information to a pilot about the degree of braking quality that can be expected (good, fair, poor, nil)



CAVOK: Ceiling and Visibility OK, visibility is 10km or more, no clouds under 5000Ft (or highest minimum sector altitude) no fog or mist, and no precipitation, thunderstorm or drifting snow.
CDI: Course Deviation Indicator, the vertical needle on the OBI which indicates deviation from the desired 
VOR radial
CEILING: The height above earth of the lowest cloud layer reported as broken, overcast or obscuration. 
CENTER: Air Route Traffic Control Center, or ARTCC, the enroute air traffic control facility. 
CLASS-A: Controlled airspace, generally any airspace between 18000' MSL up to and including FL600 (roughly 60000').
CLASS-B: Controlled airspace around the busiest airports, usually including several rings with different altitude limits and extended 20 miles from the center. 
CLASS-C: Controlled airspace around moderately busy airports, generally in two rings extended out 10 miles and up to 4000 feet.
CLASS-D: Controlled airspace around any airport with an active tower, generally extended out 5 miles and up to 2500 feet. 
CLASS-E: Any controlled airspace that does not fall under Class A through D. 
CLEARANCE: Another expression for Air traffic control clearance
CLEARANCE LIMIT: The point to where an aircraft is granted an ATC clearance
CLEARED AS FILED: Another expression for Cleared via flight-planned route
CLEARED FOR TAKE OFF: An expression used by ATC to authorize an aircraft to depart. The clearance includes the specific aircraft call sign and the latest known airport conditions.
CLEARED TO LAND: An expression used by ATC to authorize an aircraft to land. The clearance includes the specific aircraft call sign, latest known airport conditions and runway designator.
CLEARED VIA FLIGHT PLAN ROUTE: An expression used by ATC to indicate that an aircraft is cleared to proceed in accordance with the route filed in the Flight Plan. 
COMPOSITE FLIGHT PLAN: A flight plan that specifies VFR operation for part of the flight and IFR for another part.
CONTROLLED AIRSPACE: An airspace of defined dimensions within which ATC service is provided
Co-ORDINATED UNIVERSAL TIME: The time system used in aviation and given to the nearest minute given from 0000 to 2359. Written abbreviation Z or UTC. Spoken expression Zulu or Universal.
CORRECTION: An expression used in radio communication to indicate that an error has been made in the transmission and that the correction follows.
COURSE: The intended direction of flight along the ground horizontally. 
CROSSING TRACKS: Used in the application of separation, indicating tracks that converge or divert at an angle of 45 to 125 degrees.
CROSSWIND: In reference to wind conditions, a wind not parallel to the runway or the path of an aircraft.
CROSSWIND LEG: The part of the traffic pattern when the plane flies at right angles to the landing runway at the takeoff end. 
CTAF: Common Traffic Advisory Frequency, a radio frequency used at non-controlled airports for pilots to self-announce their position and intentions.


  •  DELTA

DEP: Departure Control, a function of an approach control facility providing ATC service for departing IFR and under certain conditions departing VFR aircraft.
DEVIATION: The departure from a current clearance, to avoid weather, turbulence or similar.
DEVIATION: The angular difference between Magnetic and True headings.
DH: Decision Height, the height on an ILS approach at which the pilot must decide if he can complete the approach or must do a missed approach.
DISPLACED THRESHOLD: A threshold not located at the end of the runway.
DME: Distance Measuring Equipment, radio equipment that allows the pilot to determine the distance to a navaid; usually coupled with a VOR. 
DOWNWIND LEG: The part of the landing pattern where the plane flies parallel to the runway (usually to the right of the runway) opposite the direction of landing.


  • ECHO

EAT: Expected Approach Time, the time at which an ATC expects an arriving aircraft following a delay, will be able to leave the holding fix.
EAC: Expected Approach Clearance Time
ELT: Emergency Locator Transmitter. 
ENTRY FIX: The first reporting point, determined by a navigation aid, over which an aircraft is expected to pass upon entering a control area.
ETA: Estimated Time of Arrival, the time of day when a flight is expected to be completed. 
ETD: Estimated Time of Departure, the time of day when a flight is expected to commence.
ETE: Expected Time En-route, the amount of time a flight is expected to take from beginning to end. 
EXECUTE MISSED APPROACH: An expression used by ATC to instruct a pilot on an Instrument Approach Procedure to initiate a climb, continue to the Missed Approach Point and follow the missed approach procedure as described or as assigned by ATC.
EXIT FIX: The last reporting points, determined by a navigation aid, over which an aircraft is expected to pass upon leaving a control area.
EXPEDITE: An expression used by ATC when immediate action is required by the pilot in order to avoid the development of a situation.



FAF: Final Approach Fix, a specific position ("fix") from with an instrument approach to landing is begun. 
FAP: Final Approach Point, a specific position on a non-precision instrument approach where the plane is established inbound on the final approach course. 
FINAL APPROACH SEGMENT: On an instrument approach, the segment from the final approach fix to the runway. 
FINAL: The part of the landing pattern just before the plane lands, where the plane is lined up with the runway. 
FIR: Flight Information Region
FIS: Flight Information Service
FIX: A specific geographic position, determined visually or relative to radio navaids. 
FL: Flight Level, an altitude based on standard instead of actual air pressure; used for flights climbing above the transition altitude. Flight Levels correspond to 1000 foot increments in altitude. 
FMS: Flight Management System, a computer system in large aircraft used to aid in navigation of pre-programmed routes. 
FSS: Flight Service Station, a facility that provide pilot briefings, en-route communication, NOTAMS, weather and other information.


  • GOLF

GLIDE: Slope or Path, a system providing vertical (altitude) guidance to a landing airplane; for example a VASI or ILS. 
GO-AROUND: Other expression for Overshoot
GPS: Global Positioning System, a system of navigation using a large group of satellites to determine position. 
GND: Ground Control, and ATC service provided to prevent collisions on the maneuvering area and to ensure the orderly flow of aircraft on the ground.



HAA: Height Above Airport, the height of the MDA (Minimum Descent Altitude) above the published 
airport altitude. 
HANDOFF: The process of transferring the radar identification of an aircraft target and radio communications to another controller.
HAT: Height Above Touchdown, the height of the DH (Decision Height) or MDA (Minimum Descent Altitude) above the highest runway elevation in the TDZ (Touchdown Zone). 
HDG: Heading, the direction in which the nose of the aircraft is pointed, expressed in degrees.
HEAVY: An aircraft capable of takeoff weight of 300,000 pounds or more. 
HEIGHT: Elevation above a ground referece point
HF: High Frequency, the radio frequency band between 3 and 30 MHz. 
HIGH SPEED TAXIWAY: A long radius taxiway that is designed to expedite aircraft turning off the active runway after landing traveling at high speed up to 60kts. (Also called, High Speed Exit, High Speed Turnoff, Long Radius Exit, Rapid Exit Taxiway and/or Turnoff Taxiway.
HIWAS: Hazardous In-flight Weather Advisory Service, continuous recorded hazardous weather information broadcast over certain VOR stations. 
HOLD: A procedure in which a plane flies a racetrack shaped pattern relative to a fix while awaiting clearance to proceed. 
HOLDING PATTERN: A predetermined racetrack pattern flown as part of holding procedure.
HOLDING PROCEDURE: A predetermined maneuver keeping an aircraft within a specified airspace whilst awaiting further clearance.
HOLDING STACK: Multiple aircraft holding at a common fix with Vertical separation 
HOLD SHORT: An expression used by ATC to instruct aircraft to hold away from the edge of a runway whilst waiting for permission to cross or proceed onto a runway.



IAF: Initial Approach Fix, the fixes on an instrument approach chart that identify the beginning of the initial
approach segment. 
IAP: Instrument Approach Plates, a book of charts defining instrument landing approaches. 
IAP: Instrument Approch Procedure, a series of predefined maneuvers that transfer a plane on an instrument flight to the point where a landing can be made visually. 
ICAO: International Civil Aviation Organization
IDENT: A request from ATC for a pilot to activate this function on his transponder. 
IF: Intermediate Fix, the fix that starts the intermediate approach segment of an instrument approach procedure. 
IFR: Instrument Flight Rules, the set of rules governing flight solely through the use of instruments; often used to mean weather conditions that require instrument flight. 
ILS: Instrument Landing System, a two part radio navigation system consisting of a localizer for left/right guidance and a glide slope for vertical guidance. 
IM: Inner Marker, a radio beacon used during an ILS landing approach located near the end of the runway. 
IMC: Instrument Meteorological Conditions, weather conditions that are such that instrument (IFR) flight is required. 
IMMEDIATE TAKE-OFF: An expression used by ATC to indicate the pilot is expected to taxi onto the runway and take off in one continuous movement, also called a Rolling Take-Off.
IAS: Indicated Airspeed.
INITIAL APPROACH SEGMENT: On an instrument approach, the segment between the IAF (initial approach fix) and the intermediate fix. 
INTERMEDIATE APPROACH SEGMENT: On an instrument approach, the segment between the intermediate fix and the final approach fix. 
INTERSECTING RUNWAYS: Two or more runways that cross or meet.
INTERSECTION: A defined geographic point (defined via navaids) used as a reference point during instrument flight. 
INTERSECTION: At an airport, the point where two runways, a runway and taxiway or two taxiways cross.



JET ROUTE: Air routes, usually from VOR to VOR, used to serve aircraft operating at higher Flight Levels.
JET STREAM: A stream of high-speed winds present at high altitudes.


  • LIMA

LANDING MINIMUMS: The minimum visibility (due to clouds, etc.) under which an instrument approach can be legally completed. 
LATERAL SEPARATION: The separation between aircraft at the same altitude expressed in terms of distance between tracks.
LDA: Localizer Type Directional Aid, an instrument landing aid similar to a localizer but not aligned with the runway. 
LEVEL: The vertical position of an aircraft in flight and variously height, altitude or flight level.
LF: Low Frequency, the radio frequency band between 30 and 300Khz
LOCALIZER: An instrument landing aid, used to provide horizontal alignment with the runway; similar to a VOR but with only a single radial and more accurate. 
LORAN: Longe Range Navigation, a system of ground based radio stations that can be used to determine an exact geographic location. 
LOW APPROACH: An approach at a low altitude over a runway, without the airplane actually touching down.


  • MIKE

MACH: The ratio of true airspeed to the speed of sound; varies with altitude. 
MAINTAIN: An expression used by ATC meaning that the aircraft must reach or remain at the Altitude or Flight Level specified, or that the aircraft must maintain a given minimum or maximum speed as specified.
MAP: Missed Approach Point, a point along an instrument approach at which as missed approach must be started in the required visual reference has not been seen. 
MARKER: A navaid beacon transmitting straight up, allowing a plane with the proper equipment to determine when a specific point on an instrument approach has been passed. 
MCA: Minimum Crossing Altitude, the lowest altitude at which a plane on an instrument flight can cross a specific fix. 
MDA: Minimum Descent Altitude, the lowest altitude (MSL) to which an instrument landing approach may go before visually acquiring the airport or beginning a missed approach. 
MEA: Minimum Enroute Altitude, for instrument flight the lowest altitude between navaids which assures acceptable navaid signals and safe obstacle clearance. 
MHA: Minimum Holding Altitude, the lowest altitude for a specific holding pattern which assures navaid reception and obstacle clearance. 
MIA: Minimum IFR Altitudes, minimum altitudes for instrument flight as published on IFR charts. 
MINIMUMS: weather condition requirements for a particular type of operation.
MINIMUMS: Weather conditions that determine whether flight is possible; when below minimums landing and taking off is not allowed. 
MISSED APPROACH: A predefined maneuver used when an instrument approach fails. 
MM: Middle Marker, a radio beacon along an ILS landing approach, normally located at or near the decision height. 
MOCA: Minimum Obstruction Clearance Altitude, the minimum published altitude within 22 nm of a VOR meeting obstacle clearance requirements.
MRA: Minimum Reception Altitude, the lowest altitude at which an intersection can be determined using the navaids that define the intersection. 
MSA: Minimum Safe Altitude, the minimum altitude that meets legal requirements, typically 1000 feet above obstacles.
MSL: Mean Sea Level


NAVAID: Navigational Aid, a radio transmitter such as a VOR, NDB, beacon, etc. that is used for radio navigation. 
NDB: Non-Directional Beacon, a radio navaid that simple transmits a signal usually received by a plane's ADF to determine the direction from the plane to the NDB. 
NEGATIVE: An expression used in radio communication meaning NO, Permission Not Granted or That is Not Correct.
NO COMPASS APPROACH: A radar approach or vector provided in the event of compass of directional indication malfunction. ATC instead of providing heading instructions will observe the rarar track and issue control instructions "Turn Right", "Turn Left" "Stop Turn" as required.
NONPRECISION APPROACH: An instrument approach where no electronic glide-slope is provided. 
NORTH ATLANTIC ORGANIZED TRACK SYSTEM: A variable track structure developed daily by appropriate Oceanic Area Control Centers (Gander west and Shanwick east) to create a series of minimum time tracks across the North Atlantic (NAT)
NOTAM: Notice To Airmen, news of interest to pilots regarding hazards, changes in service, procedures, etc.



OBI: Omni-Bearing Indicator, the dial that displays information from the VOR receiver radio, indicating radial, TO/FROM and glide-slope. 
OBS: Omni-Bearing Selector (course selector knob), the control used to select the radial on the OBI dial.
OBST: Obstacle, all fixed and mobile objects that are located on an area intended for the surface movement of an aircraft or that extend above a defined surface intended to protect aircraft in flight.
OCA: Obstacle Clearance Altitude, The lowest altitude above the elevation of a runway threshold used in establishing compliance with the appropriate published criteria.
OCA: Oceanic Control Area
OCL: Obstacle Clearance Limit, the height above the field elevation below which the minimum prescribed vertical clearance cannot be maintained either on approach or in the event of a missed approach.
OL: Obstacle Light, Anti Collision lights on buildings, towers, antennas or terrain close by an airfield giving visual reference to pilots.
OM: Outer Marker, a radio beacon along an ILS landing approach typically near the point where the ILS glide slope is intercepted and about 4 to 7 miles from the runway.


  • PAPA

PAPI: Precision Approach Path Indicator, similar to a VASI but using four lights to more accurately indicate the glide-slope. 
PIC: Pilot In Command, the person actually responsible for the operation of the aircraft in flight. 
PIREP: Pilot Weather Report, a report of weather conditions encountered during flight. 
POSITION AND HOLD: Taxi onto the runway, into takeoff position, but do not take off until clearance from ATC is received. 
PRECISION APPROACH: An instrument approach where electronic glide-slope guidance is provided (e.g., an ILS approach). 
PROCEDURE TURN: A maneuver used on instrument approaches to reverse direction and establish an aircraft on the intermediate approach segment or final course. 
PULL UP AND GO AROUND: An instruction given by ATC when in the controller's judgement, the aircraft landing procedure cannot safely be continued to touchdown.
PUSH BACK: An expression used to indicate the rearward movement of an aircraft being towed



QNH: Atmospheric Pressure at Mean Sea Level, in Millibars 
QFE : Atmospheric Pressure at Aerodrome Elevation, in Millibars
QNE: Atmospheric Setting at Standard Barometric Pressure
QDM: The Magnetic Track to a station, usually a NDB, but could also be used for a VOR or VHF station
QDT: The Magnetic Track outbound from a station, usually a NDB but could be used for a VOR or VHF station.



RADIAL: A magnetic bearing extending from a VOR station. 
RADAR: A radio detection device that provides information on range, azimuth or elevation of objects.
RADAR APPROACH: An approach executed by an aircraft under the direction of a radar controller.
RADAR CONTACT: Another expression for Radar Identified, used by ATC to inform a pilot that radar identification is established.
RADAR CONTROLLED AIRSPACE : A controlled airspace within which radar control service is provided.
RADAR CONTROL SERVICE : The control of aircraft by ATC through the provision of vectors or speed control or both, to establish the required separation between aircraft.
RADAR SERVICE TERMINATED: Expression used by ATC to inform a pilot that the provision of radar services has ceased.
RADAR VECTORING: Other expression for vector
REIL: Runway End Identifier Lights, a pair of white flashing strobe lights located at each corner of the end of a runway. 
REPORTING POINT: A specific fix where the position of an aircraft can be reported.
RMI: Radio Magnetic Indicator, an aircraft navigation instrument coupled with a gyro compass that indicates the direction to a navaid plus bearing with respect the aircraft heading. 
RUNWAY HEADING: the exact magnetic heading of the runway centerline to the nearest degree. 
RUNWAY NUMBER: determined from the runway magnetic heading rounded to the nearest ten degrees (i.e., a runway with a heading of 274 degrees would be runway 27). 
RVR: Runway Visual Range, the distance that a pilot can see down the runway from the approach end; needed for instrument landings in reduced visibility. 
RATE ONE-HALF TURN: The turn rate of 1.5' per second normally used by aircraft operating in 250kts or more.
RATE ONE TURN: The turn rate of 3' per second normally used by aircraft operating at less than 250kts.
RVSM: Reduced Vertical Separation Minimum. The application of 1000ft vertical separation between flight levels FL290 and FL410 between RVSM certified aircraft.



SAY AGAIN: An expression used to request a repetition of the last transmission.
SAY ALTITUDE: An expression used by ATC to request an aircraft's specific altitude or Flight Level
SECTIONAL: A chart using a scale of 1:500,000 used for VFR flight.
SEPARATION: The spacing between aircraft, altitudes, Flight Levels or Tracks.
SID: Standard Instrument Departure, a specific airport departure route usually used for instrument flights. 
SIGMET: A weather advisory concerning conditions of significant interest to all aircraft, such as severe turbulence, severe icing, etc. 
SPEED ADJUSTMENT: An ATC procedure used to request pilots to adjust speed as directed to provide the desired separation.
SQUAWK: Activate and set the aircraft's transponder to a specific four-digit code. 
SSR: Secondary Surveillance Radar, a back up system integral to the proper operation of the transponder. 
STANDARD RATE TURN: A turn of three degrees per second; also called a two minute turn because a complete circle takes two minutes to complete. 
STAR: Standard Terminal Arrival, a specific airport arrival route that begins some distance away and puts the plane into a standard instrument landing approach. 
STOP AND GO : A procedure where an aircraft will land, make a complete stop on the runway, and then take off again. 
STRAIGHT IN: An approach and landing where the normal traffic pattern is skipped and the plane intercepts the runways heading and lands straight ahead. 
SVFR: Special VFR Flight. A visual flight authorized by ATC to operate within a control zone under meteorological conditions that are bellow VFR weather conditions.



TARGET: The indication on a radar display of a primary radar echo or a transponder reply. 
TCAS: Traffic Alert and Collision Avoidance System. 
TCH: Threshold Crossing Height, the height above the runway that an aircraft should cross the runway threshold on an ILS approach. 
TDZE: Touchdown Zone Elevation, the highest elevation in the first 3000' of the landing runway. 
THRESHOLD: the beginning of the portion of the runway that is usable for landing. 
TOUCH AND GO: A practice landing where the plane touches downs, continues rolling, and takes off again. 
TOUCHDOWN ZONE: The first 3000' of the runway, beginning at the threshold. 
TRACK: The actual path of the aircraft over the surface of the earth. 
TRAFFIC PATTERN: The traffic flow of airplanes landing and taking off from an airport, consisting of upwind, crosswind, downwind, base and final legs. 
TRANSITION ALTITUDE: The Altitude above Mean Sea Level, used for departing aircraft, where the QNH needs to be set to local Atmospheric Pressure.Above the TA the aircraft altimiter pressure setting should be adjusted to the standard pressure setting and Flight Levels are used.
TRANSITION LEVEL: The Flight Level used for decending aircraft at which, the pilot start to refer to altitude of the aircraft by setting the altimeter to the QNH for the airfield or region.
TRANSPONDER: A device in a plane that responds to ground signals and returns information such as the squawk code, altitude, etc. 
TRSA: Terminal Radar Service Area, airspace surrounding certain airports where ATC provides radar vectoring, sequencing and separation.



UHF: Ultra High Frequency, the frequency band between 300 and 3000 MHz
UNABLE: An expression used indicating the inability to comply with a specific request, clearance or instruction.
UNICOM: A radio facility that may provide airport information at certain airports.
UPWIND: The part of the traffic pattern where the plane flies parallel to the landing runway in the direction of landing. 
UTC: Universal, spoken Expression for Coordinated Universal Time another expression for ZULU time.



VASI: Visual Approach Slope Indicator, a system of lights place adjacent to a runway that allow the pilot to maintain a proper glide-slope for landing. 
VECTOR: A heading given by ATC to pilots to provide navigational guidance.
VERTICAL SEPARATION: The separation between aircraft expressed in units of vertical distance.
VFR ON TOP: ATC authorization for an IFR aircraft to operate in VFR conditions at an appropriate VFR altitude above the clouds. 
VFR: Visual Flight Rules, the rules that govern flight under visual conditions; also used to indicate that weather conditions are suitable for visual flight. 
VHF: Very High Frequency, the band between 30 and 300 MHz.
VISUAL APPROACH: An approach conducted on an IFR flight plan which authorizes the pilot to proceed visually and clear of clouds to the airport. 
VISUAL DESCENT POINT: A defined point on a non-precision instrument approach from which normal descent from the MDA to the runway can be commenced. 
VMC: Visual Meteorological Conditions, weather conditions where visibility and cloud ceiling allows legal VFR flight. 
VOR: Very High Frequency Omni Directional Range Station, a ground based navigation aid transmitting VHF navigation signals, 360 degrees in azimuth, oriented from magnetic north. 
VORTAC: VHF Omni Directional Range/Tactical Air Navigation, a radio navaid providing VOR azimuth, TACAN azimuth and TACAN distance measuring (DME) at one site



WAKE TURBULENCE: Turbulent Air behind an aircraft caused by one or any of the following:

  1. Wing tip Vortices
  2.  Rotor tip Vortices
  3. Jet engine blast
  4. Rotor down-wash
  5. Propeller wash

WAYPOINT: A geographical fix position used for routing or instrument approach or reporting point.


  • ZULU

ZULU or Z: Another term for Coordinated Universal Time.

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Content updated:  7. September 2018.