# Air Traffic Simulation Framework for Testing Automated Air Traffic Control Solutions +
### Review of Existing Air Traffic Simulation Environments  
A variety of simulation tools have been developed to support ATM research, enabling the evaluation of new technologies, procedures, and policies under realistic conditions. BlueSky [12] is an open-source, multi-platform simulation tool designed to facilitate the comparison of ATM research concepts with each other, rather than solely against the current operational state. Its development was driven by the need for high-fidelity simulations without reliance on proprietary data and to promote community adoption through a user-friendly interface. BlueSky focuses on agent-based simulation and modeling and is easily modifiable and operable on simple systems. It operates based on scenarios that can be preloaded with time-stamped commands, but in this system commands can be issued dynamically during execution. AirTrafficSim [13] is another open-source, web-based simulation platform that enables microscopic analysis of air traffic movements. It supports visualization of historical data and performance evaluation of user-defined ATC algorithms. AirTrafficSim integrates weather data and provides an API for external aircraft control, supporting diverse ATM research areas such as conflict resolution, route optimization, and contingency management. The simulation mimics an autopilot system that follows a pre-defined flight plan while dynamically adopting ATC instructions including non-standard directives such as vectoring and holding. By computing aircraft performance metrics (e.g., fuel consumption, speed) at each time step, the system enables a detailed analysis of the impact of user-defined control algorithms on overall traffic flow. CASSIOPEIA [14], developed within the SESAR program, uses an agent-based modeling approach to represent the socio-technical complexity of ATM. It simulates interactions among stakeholders--such as network managers, airlines, airports, and aircraft--based on their goals, beliefs, and decision-making processes. This framework supports policymakers in evaluating the potential implications of future concepts and regulatory measures. The ELSA project [15] also adopts an agent-based approach, featuring agents such as aircraft operators, network managers, pilots, and controllers. It offers an open-source simulation environment focused on trajectory management. The network is modeled as a graph of navigation points. During the strategic phase, trajectories are de-conflicted by adjusting take-off times; in the tactical phase, conflicts are monitored and resolved dynamically, including directions based on sector capacities. Special conditions, such as the activation of Temporarily Restricted Areas or weather disruption are also incorporated. ELSA's modular architecture allows for independent use of its components and is accessible for the research community to use and modify. The model was used to assess the impact of future SESAR scenarios [15]. FACET [16], developed by NASA Ames Research Center, aims to help researchers and service providers increase airspace capacity and flexibility by simulating and analyzing aircraft trajectories in the U.S. National Airspace System. It has been used to study concepts such as Distributed Air/Ground Traffic Management, advanced Air Traffic Flow Management, and new Decision Support Tools. FACET models en-route aircraft trajectories using kinematic equations considering both aircraft type performance and weather conditions. DYNAMO [17], developed by the Universitat Politecnica de Catalunya, is a cloud-based simulation tool designed for 4D trajectory optimization. It is free to use and generates optimized flight trajectories by considering constraints related to aircraft operations, flight procedures, time, fuel, operating costs, and air navigation charges. Finally, AdAS [18] is a hybrid gate-to-gate simulation framework focused on both landslide and airside traffic flow, aiming to improve understanding of the operational dynamics of the European air traffic network.