For several years, the FAA has used the results of an airport capacity tool called the runwaySimulator model, developed by MITRE. The FAA and MITRE are now making the tool publicly available for aviation applications, including airport planning. The tool is designed to assess an airport's existing capacity, as well as capacity improvements such as new infrastructure or flight procedures. The tool replaces the FAA's Airfield Capacity Model (ACM), which is now dated.

Request Access to runwaySimulator

You can request access to the tool and related training. Completion of the training program is needed before the software is provided for use. At present, the MITRE software license is for US domestic use.

User Forum

An online KSN forum is available for users of runwaySimulator to ask questions, get help, and share tips and tricks with use of the model. Permission is required to access to the forum.


For further information, contact Kent Duffy.

About runwaySimulator

The runwaySimulator model simulates arriving and departing traffic at an airport, the decisions made about runway assignment and sequencing, and the flight operations themselves. The model generates a randomized traffic sample that keeps pressure on the airport. The traffic sample reflects an airport's mix of aircraft types, which differ in their performance parameters. Separation standards in FAA Order 7110.65, Air Traffic Control are codified as rules that govern pairs of flight operations, and these are modified to represent common pilot and controller behaviors. The runway configuration is set and exceptions noted to prohibit use of specified runways by certain aircraft types or to set aside runways for exclusive use by, say, general aviation traffic. A heuristic algorithm assigns runways and sequences traffic to balance efficiency and delay while respecting separation requirements and runway eligibilities.

When used to estimate capacity, runwaySimulator generates traffic so there is constant demand on the runway system. It does this for various arrival-departure mixes and, for each, simulates steady-state operations for several hundred hours. The average throughput achieved is recorded for each arrival-departure mix and used to create the airport's capacity "curve" (i.e., a Pareto frontier). The model provides a variety of measurements and visualizations to the analyst to verify and validate the simulation.

This screenshot of runwaySimulator shows aircraft flight tracks to and from the runways of an airport, as modeled in the software.  The screenshot also shows the graphical user interface that is used run the model.

Screenshot of the runwaySimulator software

The tool can be used to estimate runway capacity with current and future operations. However, runwaySimulator does not evaluate most non-runway constraints at the airport nor limitations elsewhere in the national airspace system. Such constraints may include taxiway or gate constrains, terminal airspace congestion, Air Traffic Control traffic management initiatives, and seasonal limitations due to high temperatures that restrict aircraft climb rates.

The software, written in Java and free of third-party license requirements, rests on two MITRE-developed foundations: the Tortuga simulation framework and the Aviation Data Library. The new version of runwaySimulator includes a newly developed fast-time version of MITRE’s Java Flight Model and a more robust trajectory engine. The software uses the Aeronautical Information Exchange Model (AIXM) Extensible Markup Language (XML) format for files describing airport layouts and procedures. In addition, the software uses the same ARINC 424 leg types found in the published procedures understood by aircraft flight management systems.

The medium resolution simulation approach has proven versatile for supporting FAA capacity assessment efforts such as the Airport Capacity Profiles and the soon-to-be-released FACT3: Airport Capacity Needs in the National Airspace System. In addition, the Airport Cooperative Research Program’s Project Report 79: Evaluating Airfield Capacity provides guidance on applicable uses of runwaySimulator for airport capacity planning. Going forward, the model will evolve based on recommendations and input from airport capacity planners and operations analysts.

The runwaySimulator Validation Report (PDF, 3.44 MB) shows simulation results align well with actual arrival and departure rates at busy airports. Validation data from the model is also provided on aircraft separations and speed profiles.