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SUBCHAPTER J—NAVIGATIONAL FACILITIES 

PART 170—ESTABLISHMENT AND 

DISCONTINUANCE CRITERIA FOR 
AIR TRAFFIC CONTROL SERVICES 
AND NAVIGATIONAL FACILITIES 

Subpart A—General 

Sec. 
170.1

Scope. 

170.3

Definitions. 

Subpart B—Airport Traffic Control Towers 

170.11

Scope. 

170.13

Airport Traffic Control Tower (ATCT) 

establishment criteria. 

170.15

ATCT discontinuance criteria. 

Subpart C 

[

Reserved

] 

A

UTHORITY

: 49 U.S.C. 106(g), 40103–40107, 

40113, 44502, 44701–44702, 44708–44709, 44719, 
44721–44722, 46308. 

S

OURCE

: 56 FR 341, Jan. 3, 1991, unless oth-

erwise noted. 

Subpart A—General 

§ 170.1 Scope. 

This subpart sets forth establishment 

and discontinuance criteria for naviga-
tion aids operated and maintained by 
the United States. 

§ 170.3 Definitions. 

For purposes of this subpart— 

Air navigation facility 

(NAVAID) 

means any facility used, available for 
use, or designated for use in the aid of 
air navigation. Included are landing 
areas; lights; signaling, radio direction- 
finding, or radio or other electronic 
communication; and any other struc-
ture or mechanism having a similar 
purpose of guiding or controlling flight 
or the landing or takeoff of aircraft. 

Air traffic clearance 

means an author-

ization by air traffic control for an air-
craft to proceed under specified traffic 
conditions within controlled airspace 
for the purpose of preventing collision 
between known aircraft. 

Air traffic control 

(ATC) means a serv-

ice that promotes the safe, orderly, and 
expeditious flow of air traffic, includ-
ing airport, approach, departure, and 
en route air traffic control. 

Air traffic controller 

means a person 

authorized to provide air traffic serv-
ice, specifically en route and terminal 
control personnel. 

Aircraft operations 

means the airborne 

movement of aircraft in controlled or 
noncontrolled airport terminal areas, 
and counts at en route fixes or other 
points where counts can be made. 
There are two types of operations: 
local and itinerant. 

(1) 

Local operations 

mean operations 

performed by aircraft which: 

(i) Operate in the local traffic pat-

tern or within sight of the airport; 

(ii) Are known to be departing for, or 

arriving from flight in local practice 
areas located within a 20-mile radius of 
the airport; or 

(iii) Execute simulated instrument 

approaches or low passes at the air-
port. 

(2) 

Itinerant operations 

mean all air-

craft operations other than local oper-
ations. 

Airport traffic control tower 

means a 

terminal facility, which through the 
use of air/ground communications, vis-
ual signaling, and other devices, pro-
vides ATC services to airborne aircraft 
operating in the vicinity of an airport 
and to aircraft operating on the airport 
area. 

Alternate airport 

means an airport, 

specified on a flight plan, to which a 
flight may proceed when a landing at 
the point of first intended landing be-
comes inadvisable. 

Approach 

means the flight path es-

tablished by the FAA to be used by air-
craft landing on a runway. 

Approach control facility 

means a ter-

minal air traffic control facility pro-
viding approach control service. 

Arrival 

means any aircraft arriving at 

an airport. 

Benefit-cost ratio 

means the quotient 

of the discounted life cycle benefits of 
an air traffic control service or naviga-
tion aid facility (

i.e.

, ATCT) divided by 

the discounted life cycle costs. 

Ceiling 

means the vertical distance 

between the ground or water and the 
lowest layer of clouds or obscuring phe-
nomena that is reported as ‘‘broken,’’ 
‘‘overcast,’’ or ‘‘obstruction.’’