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2 ELEMENTS OF THE NATIONAL AIRSPACE SYSTEM The National Airspace System is an interconnected system of airports, air traffic facilities and equipment, navigational aids, and airways. These elements of the NAS are operated and supported by airport employees, air traffic controllers, technicians, airspace specialists, and others. Airports, air traffic facilities and equipment, and navigational aids are static physical components of the NAS. Over longer periods, airports may be expanded as new runways, taxiways, and terminal buildings are built; new air traffic facilities may be built and air traffic equipment and navigational aids modernized. In contrast, the condition of the airways changes continuously, as they are affected by changing weather, winds, and traffic. This chapter describes both the static and dynamic elements of the NAS. 2.1 Airports in the United States Although there are more than 19,000 airports in the United States, over 5,000 of which are open to the public, the FAA considers only 3,367 to be significant to the capacity of the NAS. These airports are included in the National Plan of Integrated Airport Systems (NPIAS) and are eligible to receive Federal grants under the Airport Improvement Program (AIP). Within the NPIAS, the airports are divided into two major categories: commercial service airports and general aviation airports. 2 .1.1 C o m m e rcial Service Airports Commercial service (CS) airports are public airports receiving scheduled passenger service and having 2,500 or more enplaned passengers per year (an enplaned passenger is a passenger on a scheduled or unscheduled commercial flight). Figure 2-1 shows the clas- sifications of the 546 commercial service airports as well as the percentages of enplaned passengers for each class. The 422 airports that have more than 10,000 annual enplane- ments are classified as primary airports. Those commercial service airports enplaning from 2,500 to 10,000 passengers annually are classified as “other” commercial service airports. Within the primary airport classification, the term “hub” is used to identify very busy commercial service airports. This use of the term hub is different from that used in the airline industry, where a hub is an airport where passengers connect with other flights coming from the spokes of the system. The NPIAS term does not differentiate between airports with mostly connecting traffic and those with mostly origin-destination traffic. The primary airports are divided into large-hub, medium-hub, small-hub, and non-hub airports, based on the number of annual enplanements. Large-hub airports are those that account for at least one percent of total U.S. passenger enplanements. Medium hubs are airports that account for between 0.25 percent and one percent of total passenger enplanements and small hubs from 0.05 percent to 0.25 percent of total passenger enplanements. Commercial service airports that enplane less than 0.05 percent of total passenger enplanements but more than 10,000 annually are classified as non-hub primary airports.
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  • Fall '10
  • Staff
  • air traffic, General Aviation Airports, Capacity Enhancement Plan, PAC E S YS T E M, Aviation Capacity Enhancement

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