Carl Westin

1-1 Background 3 1-1 Background S INCE the dawn of air traffic control (ATC) almost a hundred years ago, air traf- fic controllers (henceforth controllers) have separated and prevented collisions between aircraft. While initially assuring safe separation during takeoff and land- ing (i.e., tower control), the responsibilities of controllers have grown to include all segments of flight between airports (e.g., terminal and en-route control). Through technological innovations such as radar and computers, the means for achieving safe separation between aircraft have changed considerably (Figure 1-1). Over the years, ATC has become increasingly dependent on technology, while the controller has maintained central responsibility. The increasingly crowded airspace is, however, affecting the nature of work and difficulty in separating traffic. In order to ascertain the safety of air travel, au- thorities aim to balance controller’s workload by regulating the flow of traffic. In en-route airspace, such capacity restrictions are primarily mandated by estimates of (a) First en-route ATC (1930s) (b) Radar equipped en-route ATC (1950s) (c) Computerized en-route ATC (1980s) (d) State-of-the-art en route ATC F IGURE 1-1: The evolution of en route ATC, spanning from the use of maps, phones, and a blackboard in the late 1930s (a), the introduction of radar in the 1950s (b), and computerized systems in the 1960-1970s, allowing for continuous monitoring of aircraft in real-time (c), up to current more automized state of the art (d).