Aviation Dictionary

This page provides a glossary of commonly used flying terms and aviation definitions. You can also peruse our list of aviation acronyms. We're always trying to improve this page, so please contact us to suggest additional flying terminology or to correct any errors.


An aircraft is "abeam" a fix, point, or object when that fix, point, or object is approximately 90 degrees to the right or left of the aircraft track. Abeam indicates a general position rather than a precise point.

absolute altitude

Absolute altitude is the height of the aircraft above the terrain over which it is flying.

Synonyms: altitude
air traffic control

Air traffic control (ATC) involves humans (typically on the ground) who communicate with aircraft to help maintain separation — that is, they ensure that aircraft are far enough apart horizontally or vertically that there is no risk of collision. Controllers may co-ordinate position reports provided by pilots, or in high traffic areas (such as the United States) they may use RADAR to see aircraft positions.

airspeed indicator

The airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the craft's airspeed, typically in knots, to the pilot.


An altimeter is an active instrument used to measure the altitude of an object above a fixed level. The traditional altimeter found in most aircraft works by measuring the air pressure from a static port. Air pressure decreases with an increase of altitude.


Altitude is the elevation of an object from a known level. In the United States and the UK aviation altitude is usually measured in feet. Everywhere else in the world the altitude is measured in metres. In aviation, the term altitude can have several meanings. It is a fundamental tenet of flight safety that both parties exchanging information concerning this topic are absolutely clear which definition is being used.

Other definitions:
True altitude
Indicated altitude
Pressure altitude
Density altitude
Absolute altitude

Synonyms: True altitude, Indicated altitude, Pressure altitude, Density altitude, Absolute altitude
approach slope

An approach slope is the path that an airplane follows on its final approach to land on a runway. It takes its name from the fact that this path is ideally a gentle downward slope. A commonly used approach slope is 3° from the horizontal. However certain airports have steeper approach paths based on the topography and buildings.

approach speed

The recommended speed contained in aircraft manuals used by pilots when making an approach to landing. This speed will vary for different segments of an approach as well as for aircraft weight and configuration.

Automatic Terminal Information Service

Automatic Terminal Information Service, or ATIS, is a continuous broadcast of recorded noncontrol information in busier terminal (i.e. airport) areas. ATIS broadcasts contain essential information, such as weather information, which runways are active, available approaches, and any other information required by the pilots, such as NOTAMs. Pilots usually listen to an available ATIS broadcast before contacting the local control tower, in order to reduce the controllers' workload and relieve frequency congestion.

The recording is updated when there is a significant change in the information, like a change in the active runway. It is given a letter designation (e.g. bravo), from the Phonetic Alphabet. The letter progresses down the alphabet and starts at Alpha each day. When contacting the control tower or ground station, a pilot will indicate he/she has "information" and the ATIS identification letter to let the controller know that the pilot is up to date with all current information.

Synonyms: ATIS

Aviation refers to flying using aircraft, machines designed by humans for atmospheric flight. More generally, the term also describes the activities, industries, and regulatory bodies associated with aircraft.

base leg

A flight path at right angles to the landing runway off its approach end. The base leg normally extends from the downwind leg to the intersection of the extended runway centerline.


In aviation the word ceiling is used to describe the height of clouds covering more than half the sky.

Certified Flight Instructor

A Certificated Flight Instructor [CFI] is authorized within the limitations of that person's flight instructor certificate and ratings to give training and endorsements.

Synonyms: CFI

see "Certified Flight Instructor"


That portion of flight operation between takeoff and the initial cruising altitude.

closed traffic

Successive operations involving takeoffs and landings or low approaches where the aircraft does not exit the traffic pattern.


A visible accumulation of minute water droplets and/or ice particles in the atmosphere above the Earth's surface. Cloud differs from ground fog, fog, or ice fog only in that the latter are, by definition, in contact with the Earth's surface.

commercial pilot

A pilot that can fly for hire.

crosswind leg

A flight path at right angles to the landing runway off its upwind end.

dead reckoning

Dead reckoning, as applied to flying, is the navigation of an airplane solely by means of computations based on airspeed, course, heading, wind direction, and speed, groundspeed, and elapsed time.

density altitude

Density Altitude is the pressure altitude adjusted for non-standard temperature.

Both increase in temperature and increase in humidity cause a reduction in air density. Thus in hot and humid conditions the density altitude at a particular location may be significantly higher than the geometric altitude. Aircraft performance depends on density altitude. On a very hot day, density altitude at an airport may be so high as to preclude takeoff, particularly for helicopters or a heavily loaded aircraft.

Synonyms: altitude
downwind leg

A flight path parallel to the landing runway in the direction opposite to landing. The downwind leg normally extends between the crosswind leg and the base leg.

emergency locator transmitter

A radio transmitter attached to the aircraft structure which operates from its own power source on 121.5 MHz and 243.0 MHz. It aids in locating downed aircraft by radiating a downward sweeping audio tone, 2-4 times per second. It is designed to function without human action after an accident.

Synonyms: ELT

Commonly used to mean that an aircraft is on the final approach course or is aligned with a landing area.

flight path

A line, course, or track along which an aircraft is flying or intended to be flown.

flight plan

Flight plans are plans filed by pilots with the local Aviation Authority (e.g. FAA in the USA) prior to flying. They generally include basic information such as departure and arrival points, estimated time, alternate airports in case of bad weather, type of flight whether instrument flight rules or visual flight rules, pilot's name and number of passengers. In most countries, flight plans are required for flights under IFR. Under VFR, they are optional unless crossing national borders, however they are highly recommended, especially when flying over inhospitable areas, such as water, as they provide a way of alerting rescuers if the flight is overdue.

global positioning system

The Global Positioning System, usually called GPS, is a satellite navigation system. A constellation of more than two dozen GPS satellites broadcasts precise timing signals by radio, allowing any GPS receiver (abbreviated to GPSr) to accurately determine its location (longitude, latitude, and altitude) in any weather, day or night, anywhere on Earth.

Synonyms: GPS
go around

A go-around is an aborted landing of an aircraft which is on final approach.

The term arises from the traditional use of circuits at airfields — a landing aircraft will first join the circuit pattern and prepare for landing in an orderly fashion. If for some reason the pilot decides not to land, he can simply fly back up to circuit height, and complete another circuit — in other words, go around again. The term go-around is still used even for modern airliners, though they may not use traditional circuit patterns for landing.

The go-around procedure may be initiated either by the air traffic control (normally the local or 'tower' controller in a controlled field) or by the pilot in command of the aircraft.

ground speed

The speed of an aircraft relative to the surface of the earth. It is the sum of the aircraft's true airspeed and the current wind and weather conditions; a headwind subtracts from the ground speed, while a tailwind adds to it.


A headwind is a wind that hits an aircraft in the front. This reduces the aircraft's ground speed and increases the time to reach a destination.


Icing occurs when water droplets in the air freeze on objects they come in contact with. This is very dangerous on aircraft, as the built up ice changes the aerodynamics of the flight surfaces, and can cause loss of lift, with a subsequent crash.


A request for a pilot to activate the aircraft transponder identification feature. This will help the controller to confirm an aircraft identity or to identify an aircraft.

indicated altitude

Indicated altitude is the reading on the altimeter.

Synonyms: altitude
instrument flight rules

Instrument Flight Rules (IFR) is a set of regulations and procedures for flying aircraft without the assumption that pilots will be able to see and avoid obstacles, terrain, and other air traffic; it is an alternative to visual flight rules (VFR), where the pilot is primarily or exclusively responsible for see-and-avoid. Since navigation and control of the aircraft under IFR is done by instruments, flying through clouds is allowed; under VFR it is not.

Synonyms: IFR
landing roll

The distance from the point of touchdown to the point where the aircraft can be brought to a stop or exit the runway.


Leasebacks are a route to airplane ownership. You purchase a plane and then lease it back to a flight school to help offset the expensive financing, insurance and maintenance costs associated with your aircraft. The flight school then has the right to rent out your plane to other pilots.

The are several downsides:

+Freedom - you now need to schedule flying time on your OWN plane - many plane owners make their purchase for *increased* freedom.

+Care - other pilots won't take care of your airplane the way you would! If you are picky about how other people treat your things than this might not be a good option for you.

+Money - you won't rich overnight doing this.

light gun

A handheld directional light signaling device which emits a brilliant narrow beam of white, green, or red light as selected by the tower controller. The color and type of light transmitted can be used to approve or disapprove anticipated pilot actions where radio communication is not available. The light gun is used for controlling traffic operating in the vicinity of the airport and on the airport movement area.

local traffic

Aircraft operating in the traffic pattern or within sight of the tower, or aircraft known to be departing or arriving from flight in local practice areas, or aircraft executing practice instrument approaches at the airport.

Part 141

Pilots may choose to be trained under Part 61 or Part 141 of the Federal Aviation Regulations [FARs].

Part 141 requires that a certified flight school provide an approved, structured course of training, which includes a specified number of hours of ground training (for example, 35 hours for Private Pilot in an airplane).

Part 141 approved schools must receive an FAA inspection and approval to conduct training under this part. A training syllabus must be written for approval as well as the flight training schedule. The aircraft must be inspected by an FAA Maintenance Inspector and approved for Part 141 instruction. The training facility must also be inspected by an FAA Operations Inspector. Training under Part 141 the student is required to complete a specific number of hours of formal ground instruction in a classroom or one on one with a FAA Certificated Flight Instructor. The flight training hours are reduced for each rating, and the total hours of flight time is reduced due to this type of training environment. However most students will exceed the minimum hours to meet the proficiency standards to pass the flight test.

Part 61

Pilots may choose to be trained under Part 61 or Part 141 of the Federal Aviation Regulations [FARs].

Part 61 sets out a list of knowledge and experience requirements, and is more suitable for students who cannot commit to a structured plan, or for training from freelance instructors.

Part 61 requires the student be able to pass the FAA written exam, with no required ground school training provided by the school. This means you may complete all the text material by yourself. If you have problems with any material you may hire an instructor to review and teach any material you are having a problem understanding. The FAA requires 40 hours of flight training as listed in Part 61.

pilot certificate

Pilot certification in the United States is under the authority of the Federal Aviation Administration (FAA). Airman Certificate or Pilot Certificate is the proper term, although the word license is commonly used, even by the FAA. Certification is regulated under parts 61 and 141 of the Federal Aviation Regulations.

Pilots are qualified to fly at a specific privilege level, and in one or more specific categories of aircraft.

Examples of privilege level include student, sport, recreational, private, commercial and transport.

pitot tube

A Pitot (pronounced p?-tó) tube is a measuring instrument used to measure fluid flow velocity, and more specifically, used to determine the airspeed of an aircraft.

pressure altitude

Pressure altitude is the elevation above a standard datum plane (typically, 1013.2 millibars).

Synonyms: altitude
private pilot

A pilot who flies for pleasure or personal business without accepting compensation for flying except in some very limited, specific circumstances.

Synonyms: private

In aviation, a spin is an aggravated stall resulting in autorotation wherein the aircraft follows a downward corkscrew path. Spins are characterized by high angle of attack, low airspeed, and high rate of descent.

One common scenario that can lead to a spin is an uncoordinated turn towards the runway. A poorly-trained pilot who is overshooting the turn to final approach will be tempted to apply rudder to increase the rate of turn while applying opposite aileron to decrease bank angle. Taken to its extreme, this maneuver will result in a fully uncoordinated turn with sufficient angle of attack to cause the aircraft to stall.

A spin has four phases.

* Entry - The pilot provides the necessary elements for the spin, either accidentally or intentionally.
* Incipient - The aircraft stalls and rotation starts.
* Developed - The aircraft's rotation rate, airspeed, and vertical speed are stabilized.
* Recovery - The angle of attack of the wings decreases below the critical angle of attack and autorotation slows. The nose steepens, after which autorotation stops.

squawk codes

Transponder codes are four digit numbers transmitted by the transponder in an aircraft in response to a secondary surveillance radar interrogation signal to assist air traffic controllers in traffic separation. A discrete transponder code (often called a squawk code) is assigned by air traffic controllers to uniquely identify an aircraft. This allows easy identity of the aircraft on radar.

1200: Visual flight rules (VFR) flight, this is the standard squawk code used in North American airspace when no other has been assigned.
7700: Emergency
7600: Lost Communications
7500: Hijack

Synonyms: transponder codes
standard rate turn

A turn of three degrees per second. On a standard rate turn, an aircraft will turn 90 degrees every 30 seconds.

static port

A static port in an aircraft is usually a small circular opening in the aircraft's skin. This opening is connected to a traditional altimeter via a tube. It is placed parallel to the (undisturbed) airflow in order to measure the static air pressure, which is used to determine the altitude of aircraft. Static port pressure is also an essential input to the airspeed indicator and vertical speed indicator.

student pilot

A pilot who is being trained by an instructor for their first full certificate, and is permitted to fly alone (solo) under specific, limited circumstances.

Synonyms: student

A tailwind is a wind that hits an aircraft from behind. This reduces the flight time by increasing the ground speed.


An operation by an aircraft that lands and departs on a runway without stopping or exiting the runway.


A terminal facility that uses air/ground communications, visual signaling, and other devices to provide Air Traffic Control [ATC] services to aircraft operating in the vicinity of an airport or on the movement area. Authorizes aircraft to land or takeoff at the airport controlled by the tower or to transit the Class D airspace area regardless of flight plan or weather conditions (IFR or VFR). A tower may also provide approach control services (radar or nonradar).


The actual flight path of an aircraft over the surface of the earth.


A term used by Air Traffic Control [ATC] to refer to one or more aircraft.

traffic advisories

Advisories issued to alert pilots to other known or observed air traffic which may be in such proximity to the position or intended route of flight of their aircraft to warrant their attention.

traffic in sight

Used by pilots to inform a controller that previously issued traffic is in sight.

traffic pattern

An airfield traffic pattern is a standard path followed by aircraft when taking off or landing.

The components of a typical traffic pattern are upwind leg, crosswind leg, downwind leg, base leg, and final approach.


A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation. In aviation, aircraft have transponders to assist in identifying them on radar and on other aircraft's collision avoidance systems.

The aviation transponder was originally developed during World War Two by the British and American military as an "Identification - Friend or Foe (IFF)" system to differentiate friendly from enemy aircraft on radar.

true altitude

True altitude is the elevation above mean sea level.

Synonyms: altitude
upwind leg

A flight path parallel to the landing runway in the direction of landing.


The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night. Visibility is reported as statute miles, hundreds of feet or meters.

visual flight rules

Visual flight rules (VFR) are a set of aviation regulations under which a pilot may operate an aircraft in weather conditions sufficient to allow the pilot, by visual reference to the environment outside the cockpit, to control the aircraft's attitude, navigate, and maintain safe separation from obstacles such as terrain, buildings, and other aircraft.

Synonyms: VFR

A waypoint is any mapped reference point useful for pilotage, which navigators can identify on land or at sea to verify their location. Natural waypoints may include natural rock formations, springs and oasis. Artificial waypoints may include buoys, lighthouses and radio beacons.

A waypoint may also be considered a fixed location with a specified longitude and latitude or UTM coordinates, which is maintained by a radio navigation system receiver such as a GPS set.