Air traffic controller

Air traffic controllers are persons who operate the air traffic control system to expedite and maintain a safe and orderly flow of air traffic and help prevent mid-air collisions. They apply separation rules to keep each aircraft apart from others in their area of responsibility and move all aircraft efficiently through 'their' airspace and on to the next.

Although the media frequently refers to them as "air controllers" no controller ever does. They are called air traffic controllers.



To understand air traffic control (ATC), one must understand the different types of air traffic control. Almost everyone is familiar with the tower located at many airports, particularly the larger and busier ones, however that is often the extent of their familiarity. In truth, tower controllers are only one part of a complex system of air traffic control that mixes and manages all kinds of aircraft; both those flying under visual flight rules (VFR; providing their own separation once more than approximately five miles from the airport) and those flying under instrument flight rules (IFR; managed and separated from other IFR flights from departure point to destination, by the ATC system).

The tower controller (called a "Local Controller") separates both VFR and IFR airplanes in his (or her) area. The controller is in radio contact with each aircraft and generally relies on visual contact with the aircraft to afford the separation (there are procedures for non-radio aircraft, but the occasions for their need are quite rare).

Most towers also have a ground controller who provides various services to pilots while they are on the ground. In addition, at the larger and busier airports, there might be another local controller, a second ground controller, as well as a clearance delivery controller (for passing on IFR clearances without cluttering up otherwise busy local or ground control frequencies), and even a pre-taxi controller.

For the VFR flight the contact with ATC often ends when leaving the tower controller's area and doesn't resume until arriving near the destination airport and contacting the tower controller there. However, the hidden (and by far, the most expensive and complex) part of ATC is in the other two types: approach control and enroute.

Approach (and departure) control can be accomplished with non-radar procedures, but is more familiar to pilots when radar is used. The facility using radar is called a TRACON, or Terminal Radar Approach CONtrol, and is usually a large, dark room partway down the tower from the cab, or in the base of the tower. Several of the TRACONs which control larger or more complex airspace (Chicago, New York, Southern California) have facilities located several miles from the airport(s) they serve.

The airspace which a TRACON controls is typically from 10,000 feet (above ground level; AGL) and below, and an approximately 40 mile radius from the airport. Obviously, the larger facilities mentioned above have concomitantly larger airspace allocations or responsibilities.

Moreover, the TRACON airspace is divided into arrival airspace, departure airspace (sometimes more than one of each) and may also have separate controllers for auxiliary airports. The larger combined TRACONS will have a similar complement for each of the major airports it serves.

All the rest of the airspace is controlled by 21 enroute facilities, or Air Route Traffic Control Centers (ARTCC), usually called "centers". The smallest of these facilities (Chicago is one of the smallest geographically, yet is the busiest in terms of traffic) may only cover 100,000 square miles, while the largest cover the better parts of five of the western states.

As in the TRACONS, the center is divided into several sectors (40 or more being a not unusual number) based on geography. In addition, center airspace is usually stratified by altitude; typically from the ground (or upper TRACON limit) to 24,000 feet (altitudes 18,000 and above are called flight levels and given in hundreds of feet, e.g. FL240 for 24,000 feet), FL240 through FL350, and FL350 and above.

Historically, enroute air traffic control was initiated by airline companies before World War II. Flights were separated by time and altitude and tracked by means of estimated times over radio beacons posted on flight progress strips arranged by time and set in a vertical bay.

Eventually the U. S. Bureau of Air Commerce took over the sytem from the airlines and created the first government air traffic control system, based on similar non-radar procedures and tracking and reporting systems.

In 1938 the Civil Aeronautics Agency was founded and took over the air traffic control system, however the procedures and techniques generally remained the same.

After the 1956 crash of two airliners over the Grand Canyon, the Federal Aviation Agency (FAA) was formed which took over the ATC system and modernization began to take place. Although tower controllers had been able to talk directly to pilots for some time, enroute controllers had to relay clearances and receive position reports through airline company dispatchers or through the FAA's Flight Service Station (FSS) operators. Radio facilities to enable controllers to talk directly to pilots were among the first improvements to be put in place.

Also, aircraft on IFR flight plans are able to proceed in visual conditions at altitudes of their choice with a clearance "on top." At the time of the Grand Canyon crash, even jet powered aircraft operating in the flight levels could get on top clearances. That procedure was a principle factor in the crash and led to "Positive Control Airspace" (PCA) FL240 and above. Because of the speeds of the aircraft involved, non-radar procedures were unwieldy (standards called for ten minutes between aircraft; some 80 miles for a typical jet), even with the development of aircraft installed Distance Measuring Equipment (DME) and the reduced separation available between DME equipped aircraft (20 miles).

The answer was RADAR (RAdio Detection And Ranging). Already installed in many approach control facilities, enroute radar was installed in the centers and by the mid 1960s most facilities had 100% radar coverage at high altitude (PCA). Although some remote or rugged areas are still without radar coverage at lower altitudes, the vast majority of IFR traffic today enjoys radar services from takeoff to landing. Aircraft are afforded five miles radar separation (three miles close to an airport), significantly increasing the capacity of the system.

Throughout the development of the ATC system, the basic tool has been the flight progress strip for most operations. The local controller may use other methods for VFR traffic, but the entire IFR system is based on the strip. On it is recorded the callsign of the flight; the type, speed, and electronic equipment of the aircraft itself; its altitude; its route of flight; and relevant times.

Up until the late 1960s, virtually all strips were handwritten. Some facilities had equipment that would mechanically process a limited number of flights, and Washington Center was using a prototype computerized strip processing system, but by 1974 automated strip processing was in place in all the enroute facilities, with data transfer capability between enroute centers; between centers and TRACONs, and between centers and FSSes.

Also in the late 1960s, automation was being developed in radar presentation also; ARTS (Automated Radar Tracking System) in the TRACONs, and what was generically called NAS (actually National Airpsace System, but commonly used as a synonym for automation in general and computerized radar processing in particular) in the centers. By the mid '70s, the ATC system was virtually completely automated in flight plan processing and radar presentation.

ATC in the 21st Century is learning to do without strips, and direct data link with some aircraft is on the horizon, but controllers still use radio and multiple types of radar to monitor the airspace under their direction. When controllers must leave their seats, the next controller immediately reviews the strips and contacts the pilots to confirm any discrepancies.

Skills and Disposition

Air traffic controllers are generally individuals with excellent spatial perception, an ability which is enhanced with training. Almost universally, trainee controllers begin work in their early twenties, and retire in their fifties. Rigid physical and psychological tests and excellent vision, hearing, speaking skills are a requirement, and controllers must remain healthy and drug-free.

Most training focuses on honing the ability to visualise, in time and space, the position of each aircraft under control. Without an inbuilt mental position for each aircraft and its relationship with others, a skill termed having the picture or having the flick, a controller could not maintain safety margins.

Controllers ensure that aircraft are neither delayed nor compromised in either the busiest or the quietest of situations. A controller's shift may alternate between frenetic activity and utter boredom.


Though trained to sustain through long periods of activity, for many hours when necessary, simple body conditions like a full bladder or an empty stomach determine durability in the 'best' controllers; brain fade is almost never the reason for needing a break. The camaraderie and collective responsibility ingrained in a controller team heightens personal and mutual awareness of controllers and their frailties. In principle, each controller knows what he can handle, or someone close by knows, and workloads will not be allowed to reach dangerous levels.

Rarely are air disasters with lives lost attributed to human errors by controllers. (See Facts and known mishaps.) Often there are procedural or technological issues which contribute, and pilots have the ultimate responsibility for their planes.


The controller viewpoint is that a human brain working extraordinarily well in all circumstances is key to success. Though years of effort and billions of dollars have been spent on computer software designed to assist air traffic control, success has been largely limited to improving the tools at the disposal of the controllers such as computer-enhanced radar. Some controllers liken the problem of replacing them to implementing 3-dimensional chess, or perhaps the Harry Potter game quidditch. The problems to consider include:

  • pieces have different speed characteristics
  • no one piece can alter speed very much
  • pieces can never stop, pause, change direction suddenly
  • pieces unexpectedly turn up in a far corner of a board


Though starting pay is modest, experienced controllers are among the highest paid employees in the US government. At one time they were paid from the same chart (General Schedule ( as most other government employees, with new hires paid as GS-7s and full performance level controllers at the busiest facilities paid at the GS-14 level. After 1997, the FAA restructured the compensation system and the current salaries, called the ATC Pay Band ATC pay (, put the highest level of pay at the ATC-12 level; above the normal General Schedule tables. Controllers work a 40 hour work week, the same as other civil service emploeyees, and have sick leave and annual leave (vacation) packages identical to other civil service employees.

Because ATC is, in most facilities, a 24 hour per day, seven day per week function, rotating shifts, rotating days off, and mandatory holiday coverage and the concomitant compensations for holiday and Sunday work can impact one's base salary. Some overtime pay can accrue, and is subject to a maximum of two hours per day and no more than a sixth day in a week; however compensatory time can sometimes be negotiated instead.


Air traffic controllers in the US are represented by the National Air Traffic Controllers Association (NATCA), which succeeded the Professional Air Traffic Controllers Organization (PATCO) after President Ronald Reagan fired striking controllers in 1981. Notably, many of the newly hired controllers are now reaching retirement age, and FAA hiring and training has not kept pace. Only the drop in air traffic following the September 11 attacks has mitigated this problem.


In the US, air traffic controllers at commercial airports handling heavies are all FAA employees. Smaller general-aviation airports are often local government employees or private contractors. For several years privatizing more of these jobs has been an issue; however, this has been vehemently opposed by the unions, ostensibly on grounds of safety.

Free Flight

There are proposals to reduce the amount of direction that intercity commercial air traffic is given by permitting pilots to engage in free flight, or the choice of best direct route to save time and fuel. Some think this will reduce air traffic control costs by eliminating controller jobs. This also is opposed by the unions.

See also

External links

es:Controlador de trnsito areo nl:Luchtverkeersleider ja:航空交通管制官


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