5/19/22 

Pilot/Controller Glossary 

AIR TRAFFIC

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 Aircraft operating in the air or on an 

airport surface, exclusive of loading ramps and 
parking areas. 

(See ICAO term AIR TRAFFIC.) 

AIR TRAFFIC [ICAO]

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 All aircraft in flight or 

operating on the maneuvering area of an aerodrome. 

AIR TRAFFIC CLEARANCE

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 An authorization by 

air traffic control for the purpose of preventing 
collision between known aircraft, for an aircraft to 
proceed under specified traffic conditions within 
controlled airspace. The pilot-in-command of an 
aircraft may not deviate from the provisions of a 
visual flight rules (VFR) or instrument flight rules 
(IFR) air traffic clearance except in an emergency or 
unless an amended clearance has been obtained. 
Additionally, the pilot may request a different 
clearance from that which has been issued by air 
traffic control (ATC) if information available to the 
pilot makes another course of action more practicable 
or if aircraft equipment limitations or company 
procedures forbid compliance with the clearance 
issued. Pilots may also request clarification or 
amendment, as appropriate, any time a clearance is 
not fully understood, or considered unacceptable 
because of safety of flight. Controllers should, in 
such instances and to the extent of operational 
practicality and safety, honor the pilot’s request. 
14 CFR Part 91.3(a) states: “The pilot in command 
of an aircraft is directly responsible for, and is the 
final authority as to, the operation of that aircraft.” 
THE PILOT IS RESPONSIBLE TO REQUEST AN 
AMENDED CLEARANCE if ATC issues a 
clearance that would cause a pilot to deviate from a 
rule or regulation, or in the pilot’s opinion, would 
place the aircraft in jeopardy. 

(See ATC INSTRUCTIONS.) 

(See ICAO term AIR TRAFFIC CONTROL 

CLEARANCE.) 

AIR TRAFFIC CONTROL

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 A service operated by 

appropriate authority to promote the safe, orderly and 
expeditious flow of air traffic. 

(See ICAO term AIR TRAFFIC CONTROL 

SERVICE.) 

AIR TRAFFIC CONTROL CLEARANCE [ICAO]

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Authorization for an aircraft to proceed under 
conditions specified by an air traffic control unit. 

Note 1: For convenience, the term air traffic control 

clearance is frequently abbreviated to clearance 
when used in appropriate contexts. 

Note 2: The abbreviated term clearance may be 

prefixed by the words taxi, takeoff, departure, en 
route, approach or landing to indicate the particular 
portion of flight to which the air traffic control clear-
ance relates. 

AIR TRAFFIC CONTROL SERVICE

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(See AIR TRAFFIC CONTROL.) 

AIR TRAFFIC CONTROL SERVICE [ICAO]

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 A 

service provided for the purpose of: 

a. 

Preventing collisions: 

1. 

Between aircraft; and 

2. 

On the maneuvering area between aircraft 

and obstructions. 

b. 

Expediting and maintaining an orderly flow of 

air traffic. 

AIR TRAFFIC CONTROL SPECIALIST

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 A person 

authorized to provide air traffic control service. 

(See AIR TRAFFIC CONTROL.) 
(See FLIGHT SERVICE STATION.) 
(See ICAO term CONTROLLER.) 

AIR TRAFFIC CONTROL SYSTEM COMMAND 
CENTER (ATCSCC)

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 An Air Traffic Tactical 

Operations facility responsible for monitoring and 
managing the flow of air traffic throughout the NAS, 
producing a safe, orderly, and expeditious flow of 
traffic while minimizing delays. The following 
functions are located at the ATCSCC: 

a. 

Central Altitude Reservation Function 

(CARF). Responsible for coordinating, planning, 
and approving special user requirements under the 
Altitude Reservation (ALTRV) concept. 

(See ALTITUDE RESERVATION.) 

b. 

Airport Reservation Office (ARO). Monitors 

the operation and allocation of reservations for 
unscheduled operations at airports designated by the 
Administrator as High Density Airports. These 
airports are generally known as slot controlled 
airports. The ARO allocates reservations on a first 

PCG A

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