2NextGen is a massive endeavor to look at every aspect affecting the safety, efficiency, predictability, and environmental factors which might impact the NAS. This includes everything from streamlining and improving individual avionics components to coordinating and predicting the movement of thousands of aircraft on a daily basis. Of course, with every change made, its effects on other parts of the system must be taken into account. Furthermore, as a vital component, humans must interact seamlessly within the system and with the system. Systems must account for, and take advantage of, strengths and weaknesses of human performance and experience, as well as differences which exist between individuals.The general purpose of this exercise is to better understand the implication of controllers' individualized techniques and strategies for managing aircraft, while using NextGen tools and automation, under conditions of elevated demand. Before discussing the differences in strategy and implications on the implementation of tools and automation in NextGen, a discussion on why this comparison might be of interest.With research involving human participants, it is generally understood that every person differs from the next. An individual's unique combination of cultural experiences, intelligence, stress, diligence, visual acuity, muscle reflexes, just to name a few, are going to shape his/her interaction with the system. In the context of an ATC environment, a single problem space may be resolved with more than one solution. 2 For example, sector configuration, traffic characteristics, workload, etc. require strategies that minimize the likelihood of controller overload or an unsafe event. 3,4 There is also literature discussing the types of clearances controllers use to manage aircraft 5 as well as different tools and automation which may be used in NextGen ATC environments. 6 These strategies employed by controllers might also vary as a combination of factors. That is, two controllers may use the tools identically under normal circumstances, but when workload increases, or some other factor changes, the strategies of the two controllers may deviate, or vice versa.Regarding the differences in individualized use of automation, Ref. 7 presented evidence that strong differences were found between pilots' strategies for using autopilot in a multitask environment. Specifically, among five pilots, three completely different strategies were developed for managing the use of the autopilot systems, none of which were predicted or intended by the autopilot designers. Similarly, research has shown the use of data communications by flight crews and ATCs 8,9 corresponds with an increase in visual and manual workload, and a decrease in auditory and speech workload. This research lends itself to the idea that when developing tools and automation for use by ATCs, it is important to understand how they will be used and that different strategies elicited by individual ATCs can lead to differences in performance.One of the biggest concern...