Accelerate-Stop Distance Available (ASDA) – See declared distances.

Air Route Traffic Control Center (ARTCC or Center) – A FAA facility established to provide air traffic control service to aircraft operating on Instrument Flight Rules (IFR) flight plans within controlled airspace during the en route portion of flight.

Air Traffic Control (ATC) – A service operated to promote the safe, orderly, and expeditious flow of air traffic.

Aircraft Approach Category (AAC) – As specified in 14 CFR Part 97 § 97.3, Symbols and Termes Used in Procedures, a grouping of aircraft based on a reference landing speed (VREF), if specified, or if VREF is not specified, 1.3 times stall speed (VSO) at the maximum certified landing weight. Expressed with a letter designation (A through E).

Airman’s Information Manual (AIM) – A publication containing basic flight information and ATC procedures, designed primarily as a pilot’s information and instructional manual for use in the National Airspace System.

Airplane Design Group (ADG) – A classification of aircraft based on wingspan and tail height. When the aircraft wingspan and tail height fall in different groups, the higher of the two is used. Expressed with a roman numeral designation (I through VI).

Airport – An area of land that is used or intended to be used for the landing and takeoff of aircraft, and includes its buildings and facilities, if any.

Airport Elevation – The highest point on an airport’s usable runways, expressed in feet above mean sea level (MSL).

Airport Improvement Program (AIP ) – A Federal funding program for airport improvements. AIP is periodically reauthorized by Congress with funding appropriated from the Aviation Trust Fund. Proceeds to the Trust Fund are derived from excise taxes on airline tickets, aviation fuel, etc.

Airport Layout Plan (ALP) – A scaled drawing of existing and proposed land and facilities necessary for the operation and development of the airport. The ALP shows boundaries and proposed additions to all areas owned or controlled by the airport operator for airport purposes, the location and nature of existing and proposed airport facilities and structures, and the location on the airport of existing and proposed non-aviation areas and improvements thereon.

Airport Operations – Landings (arrivals) and takeoffs (departures) from an airport.

Airport Reference Code (ARC) – An airport designation that signifies the airport’s highest Runway Design Code (RDC), minus the third (visibility) component of the RDC. The ARC is used for planning and design only and does not limit the aircraft that may be able to operate safely on the airport.

Airport Reference Point (ARP) – The approximate geometric center of all usable runways at the airport.

Airport Traffic Control Tower (ATCT ) – The airport traffic control facility located on an airport that is responsible for traffic separation within the immediate vicinity of the airport and on the surface of the airport.

Airway – A corridor of controlled airspace whose centerline is established by radio navigational aids (NAVAIDs). Low altitude airways (between 3,000 and 18,000 feet MSL) are identified by number with the letter V as a prefix. High altitude airways (above 18,000 feet MSL) are known as Jet airways and are identified by number with the letter J as a prefix.

Aligned Taxiway – A taxiway with its centerline aligned with a runway centerline. Sometimes referred to as an “inline taxiway”

Ambient Noise – The total sum of noise from all sources in a given place and time.

Approach Light Systems (ALS) – A series of lights that assists the pilot when aligning aircraft with the extended runway centerline on final approach.

Approach Procedure with Vertical Guidance (APV) – An Instrument Approach Procedure (IAP) with both vertical and lateral electronic guidance.

Approach Reference Code (APRC) – A code signifying the current operational capabilities of a runway and associated parallel taxiway with regard to landing operations.

Attenuation – Acoustical phenomenon whereby sound energy is reduced between the noise source and the receiver. This energy loss can be attributed to atmospheric conditions, terrain, vegetation, other natural features, and man-made features (e.g., sound insulation).

Automated Radar Terminal System (ARTS) – Computer-aided radar display subsystems capable of associating alphanumeric data – such as aircraft identification, altitude, and airspeed – with aircraft radar returns.

A-Weighted Sound (dBA) – A system for measuring sound energy that is designed to represent the response of the human ear to sound. Energy at frequencies more readily detected by the human ear is more heavily weighted in the measurement, while frequencies less well detected are assigned lower weights. A-weighted sound measurements are commonly used in studies where the human response to sound is the object of the analysis.

Azimuth – An arc of the horizon measured between a fixed point (such as true north) and the vertical circle passing through the center of an object.


Base Leg – A flight path at right angles to the approach of a runway end. It usually extends from the downwind leg to the intersection of the extended runway centerline. See “traffic pattern.”

Baseline Condition – The existing condition or conditions prior to future development or the enactment of additional noise abatement procedures, which serve as a foundation for analysis.

Blast Fence – A barrier used to divert or dissipate jet blast or propeller wash.

Blast Pad – A surface adjacent to the ends of runways provided to reduce the erosive effect of jet blast and propeller wash. A blast pad is not a stopway.

Building Restriction Line (BRL) – A line drawn on an airport layout plan, which distinguishes, between areas that are suitable for buildings and areas that are unsuitable. The BRL is drawn to exclude the runway protection zones, the runway visibility zones required for clear line of sight from the airport traffic control tower, and all airport areas with a clearance of less than 35 feet (10.5 meters) beneath the FAR Part 77 surfaces.

Bypass Taxiway – A taxiway used to reduce aircraft queuing demand by providing multiple takeoff points.


Circling Approach – A maneuver initiated by the pilot to align the aircraft with a runway for landing when a straight-in landing from an instrument approach is not possible or is not desirable.

Clearway (CWY) – A defined rectangular area beyond the end of a runway cleared or suitable for use in lieu of runway to satisfy takeoff distance requirements (see also Takeoff Distance Available [TODA])

Cockpit to Main Gear Distance (CMG) – The distance from the pilot’s eye to the main gear turn center.

Commuter Aircraft – Commuters are commercial operators that provide regularly scheduled passenger or cargo service with aircraft seating less than 60 passengers. A typical commuter flight operates over a trip distance of less than 300 miles.

Compass Calibration Pad – An airport facility use for calibrating an aircraft compass.

Controlled Airspace – Airspace of defined dimensions within which air traffic control service is provided to IFR flights and to VFR flights in accordance with the airspace classification. Controlled airspace is designated as Class A, Class B, Class C, Class D, or Class E. Aircraft operators are subject to certain pilot qualifications, operating rules, and equipment requirements as specified in FAR Part 91, depending upon the class of airspace in which they are operating.

Crossover Taxiway – A taxiway connecting two parallel taxiways (also referred to as a transverse taxiway).

Crosswind Leg – A flight path at right angles to the approach runway end off of its upwind end.


Decision Altitude (DA) – A specified altitude on a vertically-guided approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. DA is referenced to mean sea level (MSL).

Declared Distances – The distances the airport owner declares available for a turbine powered aircraft’s takeoff run, takeoff distance, accelerate-stop distance, and landing distance requirements. The distances are:

Takeoff Run Available (TORA) – The runway length available and suitable for the ground run of an aircraft taking off;

Takeoff Distance Available (TODA) – The TORA plus the length of any remaining runway or clearway beyond the far end of the TORA; the full length of the TODA may need to be reduced because of obstacles in the departure area;

Accelerate-Stop Distance Available (ASDA) – The runway plus stopway length declared available and suitable for the acceleration and deceleration of an aircraft aborting a takeoff;

Landing Distance Available (LDA) – The runway length declared available and suitable for landing an aircraft.

Departure Reference Code (DPRC) – A code signifying the current operational capabilities of a runway with regard to takeoff operations.

Design Aircraft – An aircraft with characteristics that determine thee application or airport design standards for a specific runway, taxiway, taxilane, apron, or other facilities (such as Engineered Materials Arresting System [EMAS]). This aircraft can be a specific aircraft model or a composite of several aircraft using, expected, or intended to use the airport or part of the airport. (Also called “critical aircraft” or “critical design aircraft.”)

DGPS antenna – Differential Global Positioning System is a way to correct the various inaccuracies in the GPA system by placing a reference antenna on a point that has been accurately surveyed. This antenna receives the same GPS signals as an aircraft but corrects the GPS signal for any inaccuracies.

Displaced Threshold – A threshold that is located at a point on the runway other than the designated beginning of the runway. The portion of pavement behind a displaced threshold may be available for takeoffs in both directions and landings from the opposite direction.

Distance Measuring Equipment (DME) – A flight instrument that measures the line-of-sight distance of an aircraft from a navigational radio station in nautical miles.


Easement – The legal right of one party to use part of the rights of a piece of real estate belonging to another party. This may include, but is not limited to, the rite of passage over, on or below the property; certain air rights above the property, including view rights; and the rights to any specified form of development or activity.

En Route System – That part of the National Airspace System where aircraft are operating between origin and destination airports.

En Route Control – The control of IFR traffic en route between two or more adjacent approach control facilities.

Environmental Assessment (EA) – A concise document that assesses the environmental impacts of a proposed Federal Action. It discusses the need for, and environmental impacts of, the proposed action and alternatives. An environmental assessment should provide sufficient evidence and analysis for a Federal determination whether to prepare an Environmental Impact Statement (EIS) or a Finding of No Significant Impact (FONSI). Public participation and consultation with other Federal, state, and local agencies is a cornerstone of the EA process.

Environmental Impact Statement (EIS) – An EIS is a document that provides a discussion of the significant environmental impacts which would occur as a result of a proposed project, and informs decision-makers and the public of the reasonable alternatives which would avoid or minimize adverse impacts. Public participation and consultation with other Federal, state, and local agencies is a cornerstone of the EIS process.

Entrance Taxiway – A taxiway designed to be used by an aircraft entering a runway. Entrance taxiways may also be used to exit a runway.

Exit Taxiway – A taxiway designed to be used by an aircraft only to exit a runway:

Acute-Angled Exit Taxiway – A taxiway forming an angle less than 90 degrees from the runway centerline.

High Speed Exit Taxiway – An acute-angled exit taxiway forming a 30 degree angle with the runway centerline, designed to allow an aircraft to exit a runway without having to decelerate to a typical taxi speed.


Federal Aviation Administration (FAA) – The FAA is the Federal agency responsible for insuring the safe and efficient use of the nation’s airspace, for fostering civil aeronautics and air commerce, and for supporting the requirements of national defense. The activities required to carry out these responsibilities include: safety regulations; airspace management and the establishment, operation, and maintenance of a system of air traffic control and navigation facilities; research and development in support of the fostering of a national system of airports, promulgation of standards and specifications for civil airports, and administration of Federal grants-in-aid for developing public airports; various joint and cooperative activities with the Department of Defense; and technical assistance (under State Department auspices) to other countries.

Federal Aviation Regulations (FAR) – The body of Federal regulations relating to aviation. Published as Title 14 of the Code of Federal Regulations.

Final Approach – A flight path that follows the extended runway centerline. It usually extends from the base leg to the runway.

Finding of No Significant Impact (FONSI) – If, following the preparation of an environmental assessment, the Federal Agency determines a proposed project will not result in any significant environmental impact, a finding of no significant impact (FONSI) is issued by the Federal Agency. A FONSI is a document briefly explaining the reasons why an action will not have a significant effect on the human environment and for which an EIS, therefore, is not necessary.

Fixed-Base Operator (FBO) – A business located on the airport that provides services such as hangar space, fuel, flight training, repair, and maintenance to airport users.

Flight Track Utilization – The use of established routes for arrival and departure by aircraft to and from the runways at the airport.

FMS/GPS – Flight Management System/Global Positioning System equipment onboard an aircraft takes advantage of various radio navigation and/or GPS routes to guide the aircraft.

Fixed-By-Function Navigation Aid (NAVAID) – An air navigation aid that must be positioned in a particular location in order to provide an essential benefit for aviation is fixed-by-function.

Frangible – Retains its structural integrity and stiffness up to a designated maximum load, but on impact from a greater load, breaks, distorts, or yields in such a manner as to present the minimum hazard to aircraft.


General Aviation – All non-scheduled flights other than military conducted by non-commercial aircraft. General aviation covers all local recreational flying to business transport that is not operating under the FAA regulations for commercial air carriers.

Glide Slope (GS) – Equipment in an Instrument Landing System (ILS) that provides vertical guidance to landing aircraft.

Geographic Information Systems (GIS) – An information system that is designed for storing, integrating, manipulating, analyzing, and displaying data referenced by spatial or geographic coordinates.

Global Positioning System (GPS) – A system of  satellites used as reference points to enable navigators equipped with GPS receivers to determine their latitude, longitude, and altitude. The accuracy of the system can be further refined by using a ground receiver at a known location to calculate the error in the satellite range data. This is known as differential GPS (DGPS).


Hazard to Air Navigation – An existing or proposed object that the FAA, as a result of aeronautical study, determines will have a substantial adverse effect upon the safe and efficient use of navigable airspace by aircraft, operation of air navigation facilities, or existing or potential airport capacity.

Heigh Above Airport (HAA) – The height of the circling approach descent altitude (MDA) above the airport elevation.

Height Above Threshold (HATh) – The height of the Decision Altitude (DA) or Minimum Descent Altitude (MDA) above the threshold.


Infill – Urban development occurring on vacant lots in substantially developed areas. May also include the redevelopment of areas to a greater density.

Instrument Approach Procedure (IAP) – A series of predetermined maneuvers for the orderly transfer of an aircraft under instrument flight conditions from the beginning of the initial approach to a landing, or to a point from which a landing may be made visually. It is prescribed and approved for a specific airport by a competent authority.

Instrument Departure Runway – A runway identified by the airport operator, through the appropriate FAA Airports Office, to the FAA Regional Airspace Procedures Team intended primarily for instrument departures.

Instrument Flight Rules (IFR) – That portion of the Federal Aviation Regulations (14 CFR 91) specifying the procedures to be used by aircraft during flight in Instrument Meteorological Conditions. These procedures may also be used under visual conditions and provide for positive control by ATC. (See also VFR).

Instrument Landing System (ILS) – An electronic system installed at some airports which helps to guide pilots to runways for landing during periods of limited visibility or adverse weather.

Instrument Meteorological Conditions (IMC) – Weather conditions expressed in terms of visibility, distance from clouds, and cloud ceilings during which all aircraft are required to operate using instrument flight rules (IFR).

Island – An unused paved or grassy area between taxiways, between runways, or between a taxiway and a runway. Paved islands are clearly marked as unusable, either by painting or the used of artificial turf.


Joint-Use Airport – An airport owned by the United States that leases a portion of the airport to a person operating and airport specified under Part 139.


Knots – Airspeed measured as the distance in nautical miles (6,076.1 feet) covered in one hour. (Approximately equal to 1.15 miles per hour.)


Land and Hold Short Operations (LAHSO) – An air traffic control procedure intended to increase overall airport capacity without compromising safety. LAHSO includes landing and holding short of an intersecting runway, taxiway, or some other designated point on a runway or taxiway.

Land Use Compatibility – The ability of land uses surrounding the airport to coexist with airport-related activities with minimum conflict.

Landing and Takeoff (LTO) Cycle – The time that an aircraft is in operation at or near an airport. An LTO cycle begins when an aircraft starts its final approach (arrival) and ends after the aircraft has made its climb-out (departure).

Landing Distance Available (LDA) – See Declared Distances.

Large Aircraft – An aircraft with a maximum certified takeoff weight of more than 12,500 lbs (5,670kg).

Localizer – The component of an ILS which provides lateral course guidance to the runway.


Main Gear Width (MGW) – The distance from the outer edge of the widest set of main gear tires.

Mean Sea Level (MSL) – The average height of the surface of the sea for all stages of the tide; used as a reference for elevations. Also called sea level datum.

Minimum Descent Altitude (MDA) – The lowest authorized altitude on an approach that does not have vertical guidance. MDA is referenced to mean seal level (MSL).

Missed Approach – A prescribed procedure to be followed by aircraft that cannot complete an attempted landing at an airport.

Modification to Standards – Any approved nonconformance to FAA standards, other than dimensional standards for Runway Safety Areas (RSAs), applicable to an airport design, construction, or equipment procurements project that is necessary to accommodate an unusual local condition for a specific project on a case-by-case basis while maintaining an acceptable level of safety.

Movement Area – The runways, taxiway, and other areas of an airport that are used for taxiing or hover taxiing, air taxing, takeoff, and landing of aircraft including helicopters and tilt-rotors, exclusive of loading aprons and aircraft parking areas (reference Part 139).


Narrow-body Aircraft – A commercial passenger jet having a single aisle and maximum of three seats on each side of the aisle. Common narrow-body aircraft include A320, B717, B727, B737, B757, DC9, MD80, and MD90.

National Airspace System (NAS) – The common network of U.S. airspace; air navigation facilities, equipment, services, airports, or landing areas; aeronautical charts, information, and services; rules, regulations, and procedures; technical information, manpower, and materials, all of which are used in aerial navigation.

National Environmental Policy Act of 1969 (NEPA) – The original legislation establishing the environmental review process for proposed Federal actions.

Nautical Mile – A measure of distance equal to one minute of arc on the earth’s surface (6,076.1 feet or 1,852 meters).

NAVAIDs (Navigational Aids) – Electronic and visual air navigation aids, lights, signs, and associated supporting equpment.

Navigational Fix – A geographical position determined by reference to one or more radio navigational aids.

Non-Directional Beacon (NDB) – A beacon transmitting nondirectional signals whereby the pilot of an aircraft equipped with direction finding equipment can determine his bearing to and from the station. When the radio beacon is installed in conjunction with the ILS marker, it is normally called a compass locator.

NonMovement Area – The areas of an airport that are used for taxiing or hover taxiing, or air taxiing aircraft including helicopters and tilt-rotors, but are not part of the movement area (i.e., the loading aprons and aircraft parking areas).

Non-Precision Approach – A straight-in instrument approach procedure that provides course guidance, with or without vertical path guidance, with visibility minimums not lower than ¾ mile (4000 RVR).

Non-Precision Runway – A runway (other than precision runway) with at least one end having a non-prevision approach procedure.


Object – Includes, but it not limited to, above ground structures, Navigational Aids (NAVAIDs), equipment, vehicles, natural growth, terrain, and parked or taxiing aircraft.

Object Free Area (OFA) – An area centered on the ground on a runway, taxiway, or taxilane centerline provided to enhance the safety of aircraft operations by remaining clear of objects, except for objects that need to be located in the OFA for air navigation or aircraft ground maneuvering purposes.

Obstacle – An existing object at a fixed geographical location or which may be expected at a fixed location within a prescribed area with reference to which vertical clearance is or must be provided during flight operation.

Obstacle Clearance Surface (OCS) – An evaluation surface that defines the minimum required obstruction clearance for approach or departure procedures.

Obstacle Free Zone (OFZ) – The OFZ is the three-dimensional airspace along the runway and extended runway centerline that is required to be clear of obstacles for protection for aircraft landing or taking off from the runway and for missed approaches.

Operation – A takeoff or landing by an aircraft.

Outer Fix – An air traffic control term for a point in the airspace from which aircraft are normally cleared to the approach fix or final approach course.


Parallel Taxiway – A taxiway parallel to a runway.

Dual Parallel Taxiways – Two side-by-side taxiways, parallel to each other and the runway.

Full Parallel Taxiway – A parallel taxiway extending the full length of the runway.

Partial Parallel Taxiway – A parallel taxiway extending less than the full length of the runway.

Positive Control – The separation of all air traffic within designated airspace as directed by air traffic controllers.

Precision Approach (PA) – An instrument approach procedure that provides course and vertical path guidance with visibility minimums below ¾ mile (4000 RVR).

Precision Approach Path Indicator (PAPI) – Provides visual approach slope guidance to aircraft during an approach. It is similar to a VASI but provides a sharper transition between the colored indicator lights.

Precision Runway – A runway with at least one end having a precision approach procedure.

Primary Commercial Service Airport – A commercial airport which enplanes 0.01 percent or more of the total annual U.S. enplanements.

Primary Runway – The runway on which the majority of operations take place.

Profile – The position of the aircraft during an approach or departure in terms of altitude above the runway and distance from the runway end.

Public Use Airport – An airport open to public use without prior permission, and without restrictions within the physical capabilities of the facility. It may or may not be publicly owned.


Reliever Airport – An airport which, when certain criteria are met, relieves the aeronautical demand on a busier air carrier airport.

Runup – A routine procedure for testing aircraft systems by running one or more engines at a high-power setting. Engine runups are normally conducted by airline maintenance personnel checking an engine or other on board systems following maintenance.

Runway – A defined rectangular surface on an airport prepared or suitable for the landing or takeoff of aircraft.

Runway Design Code (RDC) – A code signifying the design standards to which the runway is to be built.

Runway End Identifier Lights (REIL) – Two synchronized flashing lights, one on each side of the runway threshold, which identify the approach end of the runway.

Runway Incursion – Any occurrence at an airport involving the incorrect presence of an aircraft, vehicle, or person on the protected area of a surface designated for the landing and takeoff of aircraft.

Runway Protection Zone (RPZ) – An area at ground level prior to the threshold or beyond the runway end to enhance the safety and protection of people and property on the ground.

Runway Safety Area (RSA) – A defined surface surrounding the runway prepared or suitable for reducing the risk or damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway.

Runway Threshold – The beginning of that portion of the runway usable for landing.


Shoulder – An area adjacent to the defined edge of paved runways, taxiways, or aprons providing a transition between the pavement and the adjacent surface; support for aircraft and emergency vehicles deviating from the full-strength pavement; enhanced drainage; and blast protection.

Single event – One noise event. For many kinds of analysis, the sound from single events is expressed using the Sound Exposure Level (SEL) metric.

Slant-range distance – The distance along a straight line between an aircraft and a point on the ground.

Small Aircraft – An aircraft with a maximum certificated takeoff weight of 12,500 lbs (5070kg) or less.

Special Use Airspace – Airspace of defined dimensions identified by an area on the earth’s surface wherein activities must be confined because of their nature and/or wherein limitations may be imposed upon aircraft operations, which are not part of those activities.

Standard Instrument Departure Procedure (SID) – A planned IFR air traffic control departure procedure published for pilot use in graphic and textual form. SIDs provide transition from the terminal to the en route air traffic control structure.

Standard Terminal Arrival Route (STAR) – A planned IFR air traffic control arrival procedure published for pilot use in graphic and textual form. STARs provide transition from the en route air traffic control structure to an outer fix or an instrument approach fix in the terminal area.

Statute Mile – A measure of distance equal to 5,280 feet.

Stopway – An area beyond the takeoff runway, no less wide than the runway and centered upon the extended centerline of the runway, able to support the airplane during an aborted takeoff, without causing structural damage to the airplane, and designated by the airport authorities for use in decelerating the airplane during an aborted takeoff. A blast pad is not a stopway.


TACAN – Tactical Air Navigation. A navigational system used by the military. TACAN provides both azimuth and distance information to a receiver on board an aircraft.

Takeoff Distance Available (TODA) – See Declared Distances.

Takeoff Run Available (TORA) – See Declared Distances.

Taxilane – A taxiway designed for low speed and precise taxiing. Taxilanes are usually, but not always, located outside the movement area, providing access from taxiways (usually an apron taxiway) to aircraft parking positions and other terminal areas.

Taxiway – A defined path established for the taxiing of aircraft from one part of the airport to another.

Taxiway Design Group (TDG) – A classification of airplanes based on outer to outer Main Gear Width (MGW) and Cockpit to Main Gear distance (CMG).

Taxiway Edge Safety Margin (TESM) – The distance between the outer edge of the main gear of an airplane with its nose gear on the taxiway centerline and the edge of the taxiway pavement.

Taxiway/Taxilane Safety Area (TSA) – A defined surface alongside the taxiway prepared or suitable for reducing the risk of damage to an aircraft deviating from the taxiway.

Terminal Radar Approach Control (TRACON) – An FAA Air Traffic Control Facility which uses radar and two-way communication to provide separation of air traffic within a specified geographic area in the vicinity of one or more airports.

Terminal Radar Service Area (TRSA) – Airspace surrounding certain airports where ATC provides radar vectoring, sequencing, and separation on a full-time basis for all IFR and participating VFR aircraft.

Threshold (TH) – The beginning of that portion of the runway available for landing. In some instances, the threshold may be displaced. “Threshold” always refers to the landing, not the start of takeoff.

Threshold Crossing Height (TCH) – The TCH is the theoretical height above the runway threshold at which the aircraft’s glideslope (GS) antenna would be if the aircraft maintains the trajectory established by the Instrument Landing System (LS) GS, or the height of the pilot’s eye above the runway threshold based on a visual guidance system.

Touchdown Zone Lighting (TDZ) – A system of two rows of transverse light bars located symmetrically about the runway centerline, usually at 100-foot intervals and extending 3,000 feet along the runway.

Traffic Pattern – The traffic flow for aircraft landing and departure at an airport. Typical components of the traffic pattern include: upwind leg, crosswind leg, downwind leg, base leg, and final approach.


UNICOM – A nongovernment communication facility, which may provide airport information at certain airports. Aeronautical charts and publications show the locations and frequencies of UNICOMs.

Upwind Leg – A flight path parallel to the approach runway in the direction of approach.


Vector – Compass heading instructions issued by ATC in providing navigational guidance by radar.

Very High Frequency Omnidirectional Range (VOR) Station – A ground-based radio navigation aid transmitting signals in all directions. A VOR provides azimuth guidance to pilots by reception of electronic signals.

Very High Frequency Omnidirectional Range Station with Tactical Air Navigation (VORTAC) – A navigational aid providing VOR azimuth and TACAN distance measuring equipment (DME) at one site.

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 Approach Slope Indicator (VASI) – A visual aid to final approach to the runway threshold, consisting of two wing bars of lights on either side of the runway. Each bar produces a split beam of light – the upper segment is white, the lower is red.

Visual Flight Rules (VFR) – Rules and procedures specified in 14 CFR 91 for aircraft operations under visual conditions. Aircraft operations under VFR are not generally under positive control by ATC. The term VFR is also used in the United States to indicate weather conditions that are equal to or greater than minimum VFR requirements. In addition, it is used by pilots and controllers to indicate a type of flight plan.

Visual Meteorological Conditions (VMC) – Weather conditions expressed in terms of visibility, distance from cloud, and cloud ceiling equal to or greater than those specified in 14 CFR 91.155 for aircraft operations under Visual Flight Rules (VFR).

Visual Runway – A runway without an existing or planned instrument approach procedure.


Wide-Body Aircraft – A commercial jet with a wingspan generally greater than 155 feet and, in passenger configuration, having two aisles with 8 to 11 seats across in a row. Common wide-body aircraft include the A300, A310, B747, B767, B777, DC-10, and MD-11.

Wingspan – The maximum horizontal distance from one wingtip to the other wingtip, including the horizontal component of any extensions such as winglets or raked wingtips.