Air Navigation Facility
A facility used, available for use, or designed for use, in aid of air navigation, including--
(A) a landing area;
(B) a light;
(C) apparatus or equipment for distributing weather information, signaling, radio-directional finding, or radio or other electromagnetic communication; and
(D) another structure or mechanism for guiding or controlling flight in the air or the landing and takeoff of aircraft.
Source: U.S. Code.