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

Modern airways, like the airplane, are an American invention.  The first lighted airways were conceived in the early 1920’s by the U.S. Post Office Department and the U.S. Army.  The first transcontinental air mail flight in 1921 used bonfires lit by Post Office staff and public spirited citizens.  The first lighted airway was a 72 mile airway between Dayton  and Columbus Ohio constructed by the Army in 1921, using rotating beacons, field floodlights and flashing markers.    Under the Air Commerce Act of 1926  airways became the job of the Airways Division of the Commerce Department Bureau of Lighthouses, and in 1927 Post Office Department airways and communications were transferred to the Department of Commerce, including the transcontinental airway.   Development of radio navigation in the 1920’s was conducted by the Post Office Department , the Navy,  Army and Bureau of Standards using radio transmitters on the ground and aircraft receivers with directional antennas.  Between the Bureau of Standards, the Army and ideas from other sources a radio system developed through the 1920s that would guide an aircraft along a chosen course and require only simple airborne equipment.  With the additions of radio beacons along the airways defined by these ranges air commerce in the United States grew, even during the depression of the 1930s.  After the period of austerity for government appropriations and the assumption of airline and airport operated air traffic control functions that further competed for limited resources developments in marker beacons and antennas for four course ranges as well as visual indicators and the simultaneous transmission range provided improvements until the advent of VHF and UHF  technology and resources in the 1940s to develop the VHF omnidirectional range, transponders and distance measurement equipment.

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 nodes, 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). In order to meet evolving needs for improved navigation accuracy, integrity, and availability as well as efficiency and economy new technologies and operating procedures they support are constantly in development.  Some do not evolve beyond the laboratory, some do not succeed operationally, and others form the next generation of aviation navigation aids.  Current plans and concepts call for the use of Global Navigation Satellite System (GNSS), and its augmentations for enroute and terminal navigation and landing. Aircraft avionics continue to advance and are now enabling our modern aircraft to fly with much less reliance on the legacy ground infrastructure. This combination of technologies can provide a common, highly advanced capability for both ATC and the flight.