FACET (F uture A ir Traffic Management C oncepts E valuation T ool) is a simulation and analysis tool being developed at the NASA Ames Research Center. This paper introduces the design, architecture, functionalities and applications of FACET. The purpose of FACET is to provide a simulation environment for exploration, development and evaluation of advanced Air Traffic Management concepts. Examples of these concepts include new Air Traffic Management paradigms such as Distributed Air/Ground Traffic Management, advanced Traffic Flow Management, and new Decision Support Tools for controllers working within the operational procedures of the existing air traffic control system. FACET models system-wide en route airspace operations over the contiguous United States. The architecture of FACET strikes an appropriate balance between flexibility and fidelity. This feature enables FACET to model airspace operations at the U.S. national level, and process over 5,000 aircraft on a single desktop computer running on any of a wide variety of operating systems. FACET has been designed with a modular software architecture to facilitate rapid prototyping of diverse Air Traffic Management concepts. FACET has prototypes of several advanced Air Traffic Management concepts: airborne self-separation; a Decision Support Tool for direct routing; advanced Traffic Flow Management techniques utilizing dynamic density predictions for airspace redesign and aircraft rerouting; and, the integration of space launch vehicle operations into the U.S. National Airspace System.

This paper examines the potential benefits of transitioning from the fixed Central East Pacific routes to user-preferred routes. A minimum-travel-time, wind-optimal dynamic programming algorithm was developed and utilized as a surrogate for the actual userprovided routing requests. After first describing the characteristics of the flights utilizing the Central East Pacific routes for a five-day period, the results of both nominal and windoptimal routing simulations are presented. The average potential time and distance savings for the wind-optimal routes was 9.9 min and 36 nmi per flight, respectively. When the windoptimal routing flight plan deviations were confined within the oceanic center boundary, the average potential time and distance savings were 4.8 min and 4.0 nmi per flight, respectively. These results are likely an upper bound on the potential savings due to the location of the polar jet stream during this five-day period. Although the sector loading did not significantly change under the wind-optimal routing simulations, the number of simulated first-loss-of-separation events did, which could contribute to increased controller workload.

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A sequential optimization method is applied to manage air traffic flow under uncertainty in airspace capacity and demand. To support its testing, a decision support system is developed by integrating a deterministic integer programming model for assigning delays to aircraft under en route capacity constraints to reactively account for system uncertainties. To reduce computational complexity, the model assigns only departure controls, while a tactical control loop consisting of a shortest path routing algorithm and an airborne holding algorithm refines the strategic plan to keep flights from deviating into capacity constrained airspace. This integrated approach is used to conduct thirty-two, 6-hour fast-time simulation experiments to explore variations in the number and severity of departure controls, tactical reroutes, and airborne holding controls. Three feasible types of traffic flow controls emerged. The first type relied primarily on departure controls and strategic reroutes on the 300 to 400 nmi look-ahead horizon and worked best when rerouting occurred at a frequency of 10 to 15 minutes. The second type generated more tactical reroutes on the 200-300 nmi look-ahead horizon and required little airborne holding or pre-departure control when rerouting occurred at a frequency of 5 minutes. The last type relied heavily on airborne holding controls and infrequent updates to the weather avoidance reroutes. This last type was the least desirable solution due to the impact of its airborne holding on airspace complexity and airspace users.

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