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All those acronyms in the aircraft cockpit

What does it all mean?

Long before "LOL" and "OMG" became everyday conversation for some, we in the aviation community adopted our own abbreviated lingo. As a new aircraft owner, learning a few key terms will get you started talking like a pro in the cockpit or the cabin. Here are some of the most common terms.

Who's Who

  • ATC | Air Traffic Control
    A service provided by the FAA to promote the safe, orderly and expeditious flow of air traffic
  • AO | Aircraft Operator
    Organizations and people who own or operate the equipment, procedures and information used to support the aircraft’s overall missions
  • CFI | Certified Flight Instructor
    A pilot who's certified by the FAA to offer aircraft instruction
  • PIC | Pilot in Command
    The pilot responsible for the control and operation of the aircraft during flight
  • SIC | Second in Command
    The pilot who is designated to take over control of an aircraft under direction of the pilot in command
  • FBO | Fixed-Base Operator
    Supplier of fuel, maintenance, flight training and other services at an airport
  • FAA | Federal Aviation Administration
    An agency of the U.S. Department of Transportation responsible for ensuring the safety of civil aviation
  • FSS | Flight Service Station
    Facilities that provide pilot briefings and routine en-route communications
  • EFAS | En Route Flight Advisory Service
    Technology that provides en route aircraft with flight updates and important weather alerts
  • GA | General Aviation
    The portion of civil aviation that refers to flights other than military, scheduled airline and cargo flights

Operational Abbreviations

  • VFR | Visual Flight Rules
    Guidelines governing flights flown solely by reference to visual cues
  • IFR | Instrument Flight Rules
    Guidelines governing flights under conditions in which it’s not safe to fly using only visual references
  • VMC | Visual Meteorological Conditions
    Weather conditions that allow for VFR
  • IMC | Instrument Meteorological Conditions
    Weather conditions that require IFR
  • AVGAS | Aviation Gasoline
    Piston aircraft fuel
  • MEL | Minimum Equipment List
    A list of instruments, equipment and procedures necessary to pilot a specific aircraft
  • AIM | Aeronautical Information Manual
    Official FAA guide to basic flight information and ATC procedures
  • UNICOM | Universal Communication
    A common radio frequency used at uncontrolled (non-tower) airports for local pilot communication
  • METAR | Meteorological Aerodome Report
    Weather conditions observed at an airport
  • ATD | Actual Time of Departure
    The time a pilot takes off from an airstrip or airport
  • ETD | Estimated Time of Departure
    The time a pilot plans to take off from an airstrip or airport
  • ATA | Actual Time of Arrival
    The time a pilot lands at a destination
  • ETA | Estimated Time of Arrival
    The time a pilot plans to land at a destination
  • ATIS | Automated Terminal Information Service
    Continuous broadcast of vital information including wind direction, velocity, pressure readings and active runway assignments
  • AFM | Airplane Flight Manuals
    Documents developed by the aircraft manufacturer and approved by the FAA, containing information and instructions required to operate the aircraft
  • POH | Pilot's Operating Handbook
    Document developed by the aircraft manufacturer containing the FAA-approved AFM


  • A/C | Aircraft
    Refers to an aircraft, not air-conditioning
  • ADI | Attitude Direction Indicator
    An instrument that shows the aircraft's orientation relative to the horizon, shows the roll and pitch of the aircraft
  • DME | Distance Measuring Equipment
    An instrument that measures slant range distance from a nav aid
  • ALT | Altimeter
    An instrument that measures an aircraft's altitude
  • HDG | Heading
    The direction the aircraft's nose is pointing
  • NAV | Navigation System
    The aircraft's directional system
  • GPS | Global Positioning System
    Satellite-based navigation information
  • VSI | Vertical Speed Indicator
    An instrument that displays an aircraft's rate of climb or descent
  • OAT | Outside Air Temperature Gauge
    An instrument that displays the temperature of the air immediately outside the aircraft
  • EHSI (or HSI) | Electronic Horizontal Situation Indicator
    Combines a heading indicator instrument with course deviation indicator
  • VOR | VHF Omnidirectional Range
    Short-range, ground-based radio navigation system for aircraft

A Few Common In-Flight Terms

  • CAS | Calibrated Airspeed
    The indicated airspeed of an aircraft, corrected for position and instrument error
  • IAS | Indicated Airspeed
    A direct instrument reading not corrected for position and instrument error
  • CAT | Clear Air Turbulence
    Turbulent conditions absent of visual indicators such as clouds
  • CAVU | Ceiling and Visibility Unlimited
    Ideal flying weather
  • AGL | Above Ground Level
    Measurement of altitude above a specific land mass
  • MSL | Mean Sea Level
    The average height off the surface of the sea for all stages of tide
  • ALS | Approach Light System
    Lighting system on the approach end of the airport runway
  • AGR | Air-Ground Ranging
    Straight-line distance from the aircraft to a point on the ground