Air Traffic Control System
The combination of elements used to safely and efficiently monitor, direct, control, and guide aircraft in the United States and United States-assigned airspace, including--
(A) allocated electromagnetic spectrum and physical, real, personal, and intellectual property assets making up facilities, equipment, and systems employed to detect, track, and guide aircraft movement;
(B) laws, regulations, orders, directives, agreements, and licenses;
(C) published procedures that explain required actions, activities, and techniques used to ensure adequate aircraft separation; and
(D) trained personnel with specific technical capabilities to satisfy the operational, engineering, management, and planning requirements for air traffic control.
Source: U.S. Code.