Navigation Services

Evolution of the United States National Airspace: The Move Towards Performance-Based Navigation

• FAA's Modernization
• Performance-Based Navigation
• Satellite Navigation
• Satellite Navigations Contribution to RNAV/RNP
• The Transition from Ground-Based Navigation Aids to Satellite-Based Navigation
• Summary

Air Traffic Control (ATC) began in the U.S. in the late 1920s, pioneered by airport employees like Archie League and William “Whitey” Conrad. Prior to 1921, flights were limited to daytime under visual flight conditions. In 1921, the first experimental night flight was conducted using bonfires along the navigational route. It was only years later that these bonfires would be extinguished. Early controllers used flags and lights to signal their instructions to pilots to prevent collisions between aircraft. In 1930, Cleveland, Ohio became the first city to boast a radio-equipped control tower.

As traffic increased, the need to ensure separation of flights moving between cities grew. Pioneer air traffic controllers used maps, blackboards, and mental calculations to ensure the safe separation of aircraft traveling along designated routes. In 1940, President Franklin Roosevelt created two agencies, the Civil Aeronautics Administration (CAA) and the Civil Aeronautics Board (CAB) and placed them under the Department of Commerce (DOC). The CAA was responsible for ATC, airman and aircraft certification, safety enforcement, and airway development. The CAB was entrusted with safety rulemaking, accident investigation, and economic regulation of the airlines. To achieve this, they began to create a complex and redundant structure of air routes supported by radio beacons.

The introduction of jet airliners and a series of midair collisions spurred passage of the Federal Aviation Act of 1958 that transferred CAA functions to a new independent body, the Federal Aviation Agency. On April 1, 1967, the Federal Aviation Agency became one of several organizations within the Department of Transportation (DOT) and became the Federal Aviation Administration (FAA).

By the mid-1970s, the FAA achieved a semi-automated ATC system based on a combination of radar and computer technology. By automating certain routine tasks, the system allowed controllers to concentrate more efficiently on the vital task of aircraft separation. Data appearing directly on the controllers' scopes provided the identity, altitude, and groundspeed of aircraft carrying radar beacons. Despite its effectiveness, this system required enhancement to keep pace with increasing air traffic.

FAA’s ATC system is one piece of today’s National Airspace System (NAS). The NAS is comprised of a complex network of systems and aircraft as well as the people who certify, operate, and maintain these systems. The NAS includes more than 19,000 airports, 750 ATC facilities, and about 45,000 facilities including radars, communications switches, ground-based navigation aids, computer displays, and radios that operate unceasingly to provide safe and efficient flight services for users. Over 48,000 FAA personnel and 616,000 pilots manage over 280,000 aircraft within the NAS. Air traffic controllers can be responsible for up to 7,000 flights at any given moment, half of the world’s air traffic.

The NAS operates non-stop - 24 hours a day, every day of the year - providing safe air transportation for millions of passengers. Not only does it span the country, but also under agreement with the International Civil Aviation Organization (ICAO), the NAS extends into the Atlantic, Pacific, and Arctic oceans, and interfaces with neighboring ATC systems for international flights. The NAS supports air transportation commerce that constitutes approximately ten percent ($1.1 trillion) of the nation's gross domestic product and affects nearly 12 million jobs.

Although the U.S. has the safest aviation system in the world, we must modernize the NAS to meet the anticipated growth in air traffic, improve safety, and bring about greater efficiencies. Included in the NAS are technologies that were developed as far back as the 1940s, such as very high frequency omnidirectional ranges (VORs) and distance measuring equipment (DME). Operation and maintenance of these technologies use up valuable FAA resources. Many of these systems have far exceeded their original life expectancy. Increasing costs to operate and maintain these systems are eroding their benefits and they are redundant to newer, more efficient technologies such as the Global Navigation Satellite System (GNSS), and its augmentations. Aircraft avionics continue to advance and are now enabling our modern aircraft to fly with much less reliance on the existing ground infrastructure. This combination of technologies can provide a common, highly advanced capability for both ATC and the flight deck.