Air traffic control

Summary

Air traffic control is responsible for keeping aircraft safely separated when in transit, both on the ground and in the air. It relies heavily on technology and a highly trained professional workforce. The equipment utilized in air traffic control is continually improving as technology evolves. The latest iteration of air traffic control technology involves the replacement of ground-based radar systems with satellite-based systems.

Definition and Basic Principles

Air traffic control is the means by which separation of aircraft in flight and on the ground is maintained. This service is provided by ground-based personnel utilizing electronic systems and two-way communication. Present-day air traffic control relies primarily on radar. Radar allows air traffic controllers to identify aircraft and to determine altitude, speed, and course. This, in turn, provides the controllers the information required to maintain separation and guide aircraft to their destinations. Air traffic control is divided into three distinct entities: air traffic control towers (ATCTs), terminal radar approach control (TRACON), and air route traffic control centers (ARTCCs). Each has a distinct function, but all activities are coordinated among the sections. Flight service stations, an advisory service, are also a part of the air traffic control network.

Historically, air traffic control has been a function of government. In the United States, that responsibility falls to the Federal Aviation Administration (FAA). A number of countries, including Canada, have been experimenting with privatizing air traffic control by contracting with independent companies. In some countries, such as Brazil, air traffic control is completely under military control. In all cases, air traffic controllers must coordinate the operation of thousands of aircraft every day. For example, in the United States in 2023, air traffic controllers managed as many as fifty thousand daily air operations, including five thousand aircraft missions at any moment. Air traffic controllers have the responsibility to ensure the safety and efficiency of each operation.

Background and History

In the early days of aviation, the airplane was considered a novelty that served few useful purposes. As the number of aircraft and the performance increased, accidents became more frequent. By 1925 the US Postal Service was attempting to establish commercial passenger service by contracting with private companies to fly mail. As this service expanded, the need for some type of air traffic control became apparent.

Until the early 1930s, aircraft operated under the “see and be seen” method of collision avoidance. As the number, size, and performance of aircraft increased, this approach proved inadequate. The earliest form of air traffic control consisted of an individual positioned at the airport with red and green flags clearing aircraft to take off or land. This system was impractical for use at night or in bad weather. The Cleveland airport was the first to establish a modern type of air traffic control in 1925 which included two-way radio communication.

In 1934, the Bureau of Air Commerce was assigned the responsibility of controlling air traffic on the newly established airways. In 1937, the Department of Commerce took over the air traffic control function. Following a number of midair collisions, the Civil Aeronautics Authority (CAA) was created. Twenty-three airway traffic control centers were established. Following World War II, the use of radar was implemented. Improved radar systems remain the primary method of controlling traffic to date, although satellite systems are being introduced.

How It Works

The entire air traffic control system relies on radar, two-way radio communication, electronic navigation aids, and highly trained professional personnel.

Air Route Traffic Control Centers (ARTCCs). The air traffic control system is divided into twenty-two ARTCCs that manage traffic within specific geographical areas. The ARTCCs are responsible for all traffic other than that controlled by the terminal radar approach control (TRACON) and the control tower facilities. Primarily utilizing constant radar surveillance, the ARTCCs provide separation for aircraft operating in controlled airspace under instrument flight rules.

ARTCCs control traffic traveling between airports. When an aircraft departs the geographical area of responsibility of one ARTCC, it is handed off to the next ARTCC along its flight route. The next ARTCC will control the aircraft until it is handed off to the next ARTCC or a TRACON facility.

Terminal Radar Approach Control. The TRACON controller accepts the aircraft from the ARTCC as it approaches within thirty to fifty miles of its destination. Again, depending primarily on radar, the TRACON controller issues instructions to the pilot sequences aircraft for approach or departure and provides separation between aircraft within the controlled airspace. The TRACON controller will hand off the traffic either to an ARTCC if the aircraft is departing or to a local controller at an air traffic control tower (ATCT) if it is landing.

Air Traffic Control Towers. The ATCT will clear the aircraft to land or take off. The tower controller, using primarily visual contact with the aircraft, will also provide all the necessary information to the pilot, such as the runway in use, the current altimeter setting, winds, ceiling and visibility, and the aircraft's position number in the landing or takeoff sequence.

Ground Control. The ATCT provides additional services while the aircraft is on the ground. The tower typically hands off a landed aircraft to a ground controller. The ground controller accepts responsibility for the aircraft as soon as it clears the active runway. Even though the aircraft is on the ground, two-way communication is still required. This is important since an aircraft on the ground could taxi onto or across an active runway and cause an accident. At larger airports ground-surveillance radar is used to direct the aircraft in taxiing.

Clearance Delivery. The last function of the ATCT is that of clearance delivery. When an aircraft is preparing to begin a flight under an instrument flight plan, the pilot must receive clearance prior to moving the aircraft. Clearance delivery will inform the pilot of the approved route, altitude, radio frequencies, and departure procedures prior to handing the pilot over to ground control for taxi instructions.

Flight Service Stations. The final component of the air traffic control structure is flight service. Flight service is an advisory-only function whereby the pilot can receive a weather briefing and file a flight plan. Flight service is also available to aircraft in flight for updated weather forecasts or to file a flight plan. Flight service can also lend assistance to aircraft in distress or pilots who become lost.

Coordination of Services. A typical scenario for a flight involves contacting flight service for a weather briefing and filing a flight plan. This would be followed by monitoring the airport terminal information frequency for automated weather and airport conditions. The pilot then contacts clearance delivery and receives the approved flight plan. After confirming the details of the flight plan, the pilot contacts ground control for taxi clearance. Ground control turns the aircraft over to the control tower for takeoff clearance. After takeoff, the aircraft is handed off to departure control. As the aircraft approaches the limits of the area covered by departure control, it is turned over to the ARTCC, which controls the aircraft until it approaches its destination. The aircraft is then handed over to approach control, followed by the control tower, and finally, ground control. Throughout this entire procedure, the aircraft would be under positive air traffic control and typically would be under radar surveillance.

Applications and Products

Modern air transportation could not exist without a highly developed and efficient system of air traffic control. The constantly developing technology allows controllers to guide the ever-increasing number of aircraft flying at any given time. There are differences, but virtually every country has an air traffic control system that is compatible with others. While some developing countries do not have the level of sophistication and may lack full radar coverage, the systems are standardized under international agreements.

Radar. With the advent of jet transport aircraft in the 1950s, an improved system of controlling these larger, faster aircraft was needed. Radar had been developed during World War II to identify approaching enemy aircraft so that fighters could be launched and directed to intercept the approaching aircraft. This system was effective from a military perspective, but the requirements for air traffic control and aircraft separation were quite different from the military application.

Air Route Surveillance Radar (ARSR). In 1956, ARSR, the first radar system specifically designed for tracking and separating civilian aircraft, was developed. Twenty-three of these units were ordered for the ARTCCs. Simultaneously, the first air traffic control computer system was installed at the Indianapolis International Airport. During the following twenty years, computer-generated display systems were incorporated into the ARSR systems. This display depicted the aircraft identification, altitude, and airspeed. It also computed the aircraft flight path and indicated possible conflicts. The aircraft signal flashed as it approached the limits of the controller's airspace so it could be safely handed off to the next controller. Because of the differing requirements of the ARTCC and TRACON, two entirely different systems were designed. The system used by ARTCCs is called radar data processing, while the system used in approach control and the tower is called automated radar terminal system (ARTS).

En Route Automation Modernization (ERAM). ERAM is a computer system that provides functionality for air traffic controllers and supports satellite-based systems such as Automatic Dependent Surveillance-Broadcase (ADS-B) and Data Communication. These systems work together to enhance safety and improve efficiency. ERAM has doubled the capacity of past air traffic control systems. It enables en route controllers at each of twenty air traffic control centers to track 1,900 aircraft at a time.

Next Generation Air Transportation System (NextGen). NextGen is a series of initiatives designed to make the airspace more efficient. It is a satellite-based system that uses digitally transmitted information in place of air traffic control. When it is fully operational, weather information will be embedded in transmitted information to assist the pilot with decision-making. NextGen not only increases safety and efficiency but also eliminates most of the problems that exist with ground-based systems, which have limited capacity, are antiquated, and are difficult to maintain.

NextGen is projected to reduce aircraft delays by 21 percent, reduce fuel consumption by 1.4 billion gallons, and reduce CO₂ emissions by 14 million tons. The FAA estimates that the total economic benefit will exceed $22 billion. The FAA plans to have all major components in place by 2025.

One integral component of the new system is the aircraft-based equipment automatic dependent surveillance-broadcast (ADS-B). This system is far more accurate than ground-based radar, and it provides the pilot with terrain maps, traffic information and location, weather, and critical flight information.

The satellite-based components of NextGen are expected to provide aircraft with the capability to fly shorter, more direct, and thus more efficient routes. It will also increase the capacity of existing runways to handle traffic and reduce delays as well as aircraft noise. At Dallas/Fort Worth International Airport alone, the FAA projects a 45 percent reduction in departure delays and an increase of ten additional departures per hour per runway when the system is in place. This is extremely important given the finite capacity of runways to handle traffic, particularly in poor weather, as well as the virtual impossibility of constructing new commercial airports.

Yet another component of NextGen is system-wide information management (SWIM). SWIM is a streamlined network over which NextGen information will be exchanged. SWIM will provide secure information-management architecture for sharing national airspace data utilizing off-the-shelf hardware and software.

Another innovation projected to have a widespread impact is artificial intelligence (AI). In the mid-2020s, developmental AI projects were underway to assist with all facets of air transit. AI is particularly adept at employing large-scale data sets such as flights, weather, flight plans, and aircraft separation, and producing outputs such as predictive analysis. Such employment may help reduce the factor of human error that is inherent in air traffic control.

Careers and Course Work

The demand for qualified air traffic controllers is expected to grow at a rate of 4 percent between 2020 and 2030. This growth can be attributed to the limited number of potential employers. In the United States, except for a few private companies staffing nonfederal control towers, the FAA is the sole employer. In some countries, the military handles all air traffic control, while some countries have contracted with private companies to run the air traffic control system. In all cases, air traffic controllers must be highly competent in areas such as communication, decision-making, planning, and weather analysis.

The major portion of an air traffic controller's training typically takes place at the FAA Academy in Oklahoma City. In the United States, a number of colleges and universities are approved to provide initial training for potential controllers. This program is called the Air Rraffic-Collegiate Training Initiative (AT-CTI) and utilizes an approved curriculum to prepare candidates for the FAA Academy. The curricula typically include courses in theory of flight, aviation laws and regulations, aviation weather, navigation, instrument flight fundamentals, and basic air traffic control. Many also include topics in crew resource management and air traffic control computer simulations. AT-CTI candidates are required to complete at least a bachelor's degree to be eligible for employment. Historically, the FAA has hired former military controllers and even some candidates with no background or training in aviation. This process is changing, and more emphasis is being placed on the AT-CTI programs to meet the needs of training new controllers.

In the mid-2020s, air traffic control was a lucrative profession and one subject to high demand. In 2023, the FAA accellerated its hiring of ATC personnel. Despite this increase in numbers, the FAA found it still had a shortfall of about 3,000 controllers. The new hires had simply replaced those retiring or that had not completed training.

Social Context and Future Prospects

Given the globalization of industry and transportation, an efficient worldwide air traffic control network is critical. Every year, the number of air travelers and air freight increases. More than four billion passengers fly annually. Many countries, such as China, are on the cutting edge of developing high-technology air traffic control networks similar to NextGen. While in 2015, the FAA was projecting the annual growth rate of air traffic in the United States to be 2 percent over twenty years, China's commercial aviation segment had grown at a rate of 7.3 percent and India's had grown at 5.9 percent in 2014. By 2020, twenty-five thousand new commercial aircraft had entered service, 31 percent of which were destined for the fast-growing Asia Pacific market. As more aircraft fill the skies, the technology required to manage these aircraft successfully becomes more complex. This situation will result in increased emphasis on air traffic control and the associated technological development.

Bibliography

"Air Traffic Controllers." Occupational Outlook Handbook, 22 Oct. 2021, www.bls.gov/ooh/transportation-and-material-moving/air-traffic-controllers.htm. Accessed 16 Feb. 2022.

FAA Aerospace Forecast: Fiscal Years 2015–2035. Federal Aviation Administration, 2015, www.faa.gov/data‗research/aviation/aerospace‗forecasts/media/2015‗national‗forecast‗report.pdf. Accessed 28 Oct. 2016.

Gleim, Irvin N., and Garrett W. Gleim. FAR/AIM: Federal Aviation Regulations and the Aeronautical Information Manual. Gleim, 2011.

Illman, Paul E. The Pilot's Air Traffic Control Handbook. 3rd ed., McGraw-Hill, 1999.

Montgomery, Jeff, ed. Aerospace: The Journey of Flight. Civil Air Patrol National Headquarters, 2008.

Nolan, Michael S. Fundamentals of Air Traffic Control. 5th ed., Delmar, 2010.

"Office of NextGen." Federal Aviation Administration, United States Department of Transportation, www.faa.gov/about/office‗org/headquarters‗offices/ang. Accessed 16 Feb. 2022.

Preston, Edmund, ed. FAA Historical Chronology: Civil Aviation and the Federal Government, 1926–1996. Department of Transportation, 1998.

Robbins, Billy D. Air Cops: A Personal History of Air Traffic Control. iUniverse, 2006.

Wallace, Gregory. “FAA Still Short about 3,000 Air Traffic Controllers, New Federal Numbers Show.” CNN, www.cnn.com/2024/05/14/business/faa-short-on-air-traffic-controllers/index.html Accessed 2 June 2024.

Weisman, Hannah. “Revolutionizing Air Traffic Control Using AI.” Arizona State University, 19 Oct. 2023, news.asu.edu/20231019-revolutionizing-air-traffic-control-using-ai.  Accessed 2 June 2024.