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.
Cosmoteer: Starship Architect and Commander - Cosmoteer: Starship Architect and Commander published and developed by Walternate Realities is a Strategy, Single-player, and Multiplayer Simulation.
GeoFS - Free, Web based flight simulator with worldwide satellite images.
Rover Builder - Rover Builder developed and published by Hatfuls Games is a Building, Strategy, and Single-player Simulation.
X-Plane - The world's most advanced flight simulator just got an upgrade. Download the free demo today for Windows, macOS, & Linux.
CATS: Crash Arena Turbo Stars - CATS: Crash Arena Turbo Stars brought by ZeptoLab is an Action, Single-player, and Multiplayer video game.