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Pilot/Controller Glossary 

of these activities. An AHA is designated via NOTAM as either a TFR or stationary ALTRV. Unless otherwise 

specified, the vertical limits of an AHA are from the surface to unlimited. 

(See CONTINGENCY HAZARD AREA.) 
(See REFINED HAZARD AREA.) 
(See TRANSITIONAL HAZARD AREA.) 

AIRCRAFT WAKE TURBULENCE CATEGORIES

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 For the purpose of Wake Turbulence Recategorization 

(RECAT) Separation Minima, ATC groups aircraft into categories ranging from Category A through Category 

I, dependent upon the version of RECAT that is applied. Specific category assignments vary and are listed in 

the RECAT Orders. 

AIRMEN’S METEOROLOGICAL INFORMATION (AIRMET)

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A concise description of an occurrence or 

expected occurrence of specified en route weather phenomena that may affect the safety of aircraft operations, 

but at intensities lower than those that require the issuance of a SIGMET. An AIRMET may be issued when any 

of the following weather phenomena are occurring or expected to occur: 

a. 

Moderate turbulence 

b. 

Low

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level windshear 

c. 

Strong surface winds greater than 30 knots 

d. 

Moderate icing 

e. 

Freezing level 

f. 

Mountain obscuration 

g. 

IFR 

(See CONVECTIVE SIGMET.) 
(See CWA.) 
(See GRAPHICAL AIRMEN’S METEOROLOGICAL INFORMATION.) 
(See SAW.) 
(See SIGMET.) 
(Refer to AIM.) 

AIRPORT

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 An area on land or water that is used or intended to be used for the landing and takeoff of aircraft 

and includes its buildings and facilities, if any. 
AIRPORT ADVISORY AREA

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The area within ten miles of an airport without a control tower or where the 

tower is not in operation, and on which a Flight Service Station is located. 

(See LOCAL AIRPORT ADVISORY.) 
(Refer to AIM.) 

AIRPORT ARRIVAL RATE (AAR)

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 A dynamic input parameter specifying the number of arriving aircraft 

which an airport or airspace can accept from the ARTCC per hour. The AAR is used to calculate the desired 

interval between successive arrival aircraft. 
AIRPORT DEPARTURE RATE (ADR)

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 A dynamic parameter specifying the number of aircraft which can 

depart an airport and the airspace can accept per hour. 
AIRPORT ELEVATION

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 The highest point of an airport’s usable runways measured in feet from mean sea level. 

(See TOUCHDOWN ZONE ELEVATION.) 
(See ICAO term AERODROME ELEVATION.) 

AIRPORT LIGHTING

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Various lighting aids that may be installed on an airport. Types of airport lighting 

include: 

a. 

Approach Light System (ALS)

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 An airport lighting facility which provides visual guidance to landing 

aircraft by radiating light beams in a directional pattern by which the pilot aligns the aircraft with the extended 

centerline of the runway on his/her final approach for landing. Condenser-Discharge Sequential Flashing 

Lights/Sequenced Flashing Lights may be installed in conjunction with the ALS at some airports. Types of 

Approach Light Systems are: 

PCG A

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