FlightGear - The FlightGear flight simulator project is an open-source, multi-platform, cooperative flight simulator development project. It also simulates space flight in Earth's orbit. It's flight dynamics engine (JSBSim) is used in a 2015 NASA benchmark.
X-Plane - The world's most advanced flight simulator just got an upgrade. Download the free demo today for Windows, macOS, & Linux.
GeoFS - Free, Web based flight simulator with worldwide satellite images.
Digital Combat Simulator - Digital Combat Simulator is a Free-to-play, Single and Multiplayer Combat Flight Simulation developed by Eagle Dynamics and published by The Fighter Collection.
esports for engineers - An award-winning strategy game for each day of the week, with daily and cumulative weekly score to help you improve. Games include classic flight and racing sims, deep learning Chess and Go, Contract Bridge. Sims take place in historical settings.
Air Combat - Air Combat is an Action, Open World, Single, and Multiplayer Combat Flight Simulation created and published by Namco.