Though technically considered under the GA umbrella, the increasing use of sophisticated, IFR-equipped aircraft by businesses and corporations has created a niche of its own. By using larger high performance airplanes and equipping them with the latest avionics, the business portion of the GA fleet has created demands for ATC services that more closely resemble commercial operators than the predominately VFR general aviation fleet.


The tendency of GA aircraft owners to upgrade the performance and avionics of their aircraft increases the demand for IFR services and for terminal airspace at airports. In response, the FAA has increased the extent of controlled airspace and improved ATC facilities at major airports. The safety of mixing IFR and VFR traffic is a major concern, but the imposition of measures to separate and control both types of traffic creates more restrictions on airspace use and raises the level of aircraft equipage and pilot qualification necessary for access.


From an operational point of view, military flight activities comprise a subsystem that must be fully integrated within NAS. However, military aviation has unique requirements that often are different from civil aviation users. The military’s need for designated training areas and low-level routes located near their bases sometimes conflicts with civilian users who need to detour around these areas. In coordinating the development of ATC systems and services for the armed forces, the FAA is challenged to achieve a maximum degree of compatibility between civil and military aviation objectives.


FAA figures show that the NAS includes more than 18,300 airports, 21 ARTCCs, 197 TRACON facilities, over 460 air traffic control towers (ATCTs), 58 flight service stations and automated flight service stations (FSSs/AFSSs), and approximately 4,500 air navigation facilities. Several thousand pieces of maintainable equipment including radar, communications switches, ground-based navigation aids, computer displays, and radios are used in NAS operations, and NAS components represent billions of dollars in investments by the government. Additionally, the aviation industry has invested significantly in ground facilities and avionics systems designed to use the NAS. Approximately 47,000 FAA employees provide air traffic control, flight service, security, field maintenance, certification, system acquisition, and other essential services.

Differing levels of ATC facilities vary in their structure and purpose. Traffic management at the national level is led by the Command Center, which essentially “owns” all airspace. Regional Centers, in turn, sign Letters of Agreement (LOAs) with various approach control facilities, delegating those facilities chunks of airspace in which that approach control facility has jurisdiction. The approach control facilities, in turn, sign LOAs with various towers that are within that airspace, further delegating airspace and responsibility. This ambiguity has created difficulties in communication between the local facilities and the Command Center. However, a decentralized structure enables local flexibility and a tailoring of services to meet the needs of users at the local level. Improved communications between the Command Center and local facilities could support enhanced safety and efficiency while maintaining both centralized and decentralized aspects to the ATC system.


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