Introduction
“Cognitive Complexity,” or the cognitive difficulty of controlling an air traffic situation, is a limiting factor on the Air Traffic Control (ATC) system. Future ATC systems such as NextGen [1] are proposing new techniques and Concepts of Operations (Con-Ops). As a result, the role and task of human agents (e.g. controllers, pilots) will be changed; however, the cognitive complexity of controllers is expected to continue to be a major functional limitation on the capacity of Air Traffic Control (ATC) system.