TRANSPORTATION - BTS - Bureau of Transportation Statistics

Aviation TechnologyThe U.S. National Airspace System (NAS) is the largest, busiest, most complex, and mosttechnologically advanced aviation operation in the world (box 6-7). The FAA provides theNAS infrastructure to support all air operations within the United States and certain oceanregions. FAA responsibility extends from air traffic control (ATC) to aviation safety andsecurity and international coordination.Box 6-7What is NAS?The National Airspace System (NAS) is a complex collection of facilities, systems, equipment,procedures, and airports. It includes more than 18,770 airports, 21 air route traffic controlcenters, 194 terminal radar approach control (TRACON) facilities, more than 467 airport trafficcontrol towers, 76 flight service stations, and approximately 4,533 air navigation facilities. Morethan 34,000 pieces of maintainable equipment, including radars, communications switches,ground-based navigation aids, computer displays, and radios are used in NAS operations. NASoperates nonstop, 24 hours a day, 365 days a year.Source: U.S. Department of Transportation, Federal Aviation Administration, FAA Administrator Fact Book(Washington, DC: December 1999).U.S. commercial aviation has been growing rapidly over the last quarter century and isprojected to grow even faster during the next 25 years. To accommodate this growth and toenhance current safety and efficiency levels, the FAA is engaged in a comprehensive programto modernize the ATC system. This includes replacing radar surveillance systems; modernizingvoice communication systems; and introducing enhanced automation aids, data links,and improved weather systems.In addition to ATC modernization (which will safely and efficiently move the increasing airtraffic and reduce congestion in the skies), new aircraft technologies are under developmentthat will allow better use of existing infrastructure capacity.During the 1970s, the ATC infrastructure needed to handle this growth in demand alsoneeded modernization. At that time, the ATC system was a combination of equipment,techniques, procedures, and skills that had evolved over the previous four decades. On onehand, it was the safest, most efficient ATC system in the world. On the other hand, it was veryexpensive to operate and maintain; expansion capability was limited at major airports; andadaptability to evolutionary change was constrained.By 1973, the NAS “En Route Stage A” Phase One modernization had been completed. Thiswas a decade-long program to automate and computerize the nation’s en route air trafficcontrol system for commercial aviation. All 21 air route traffic control centers in the UnitedStates gained the capability to automatically collect and distribute information about eachaircraft’s course and altitude to all of the sector controllers along its flight path.General aviation and military pilots still had to file flight plans at flight service stations andmilitary operations offices, but computers would then handle the centers’ “bookkeepingfunctions” of assigning and printing out controller flight strips. The new computers also hadthe ability to record and distribute any changes registered in aircraft flight plans en route.Eventually, the system was tied in with the new Automated Radar Terminal Systems beinginstalled at major airports. In 1975, phase two of the En Route Stage A automation programprovided controllers at the 21 air route traffic control centers with new radar displays, whichprovided vital flight information, such as altitude and speed, on the screen.During the last 25 years, the federal government has made impressive strides in its technologyplanning methodology and approaches. It has encouraged NAS users (airlines, pilots, U.S.6-24