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- 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]- 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- 

(See AIR TRAFFIC CONTROL.) 

AIR TRAFFIC CONTROL SERVICE [ICAO]- 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- 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)- 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 come, first served basis determined by the time the request is received at the ARO. 

(Refer to 14 CFR Part 93.) 

(See CHART SUPPLEMENT U.S.) 

c. U.S. Notice to Airmen (NOTAM) Office. Responsible for collecting, maintaining, and distrib- uting NOTAMs for the U.S. civilian and military, as well as international aviation communities. 

(See NOTICE TO AIRMEN.) 

d. Weather Unit. Monitor all aspects of weather for the U.S. that might affect aviation including cloud cover, visibility, winds, precipitation, thunderstorms, icing, turbulence, and more. Provide forecasts based on observations and on discussions with meteorolo- gists from various National Weather Service offices, FAA facilities, airlines, and private weather services. 

AIR TRAFFIC SERVICE- A generic term meaning: 

a. Flight Information Service. 

b. Alerting Service. 

c. Air Traffic Advisory Service. 

d. Air Traffic Control Service: 

1. Area Control Service, 

2. Approach Control Service, or 

3. Airport Control Service. 

AIR TRAFFIC SERVICE (ATS) ROUTES - The term “ATS Route” is a generic term that includes “VOR Federal airways,” “colored Federal airways,” “jet routes,” and “RNAV routes.” The term “ATS route” does not replace these more familiar route names, but serves only as an overall title when listing the types of routes that comprise the United States route structure. 

AIRBORNE- An aircraft is considered airborne when all parts of the aircraft are off the ground. 

