YS Flight Simulator is an open-source, realistic flight simulator game for Windows and Mac OS X. It features accurate aerodynamic models for aircraft, realistic scenery, and realistic flight physics. Players can fly a variety of aircraft, from small private jets to large commercial airlines, from modern jets to classic warbirds. Players can also fly in a variety of environments, including the open skies, in various cities, and even in outer space. The game also features a multiplayer mode for up to 16 players. YS Flight Simulator is a great way to learn the basics of flying and hone your flying skills in a safe and realistic environment.
Discontinued No longer in development. Microsoft Flight multiplayer servers were shut down on October 14, 2014.
Discontinued Last updated: 2013-04-24: https://sourceforge.net/projects/gl-117/
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Microsoft discontinued confirmed the closure of the ACES studio, the development team of Flight Simulator, on January 26, 2009. Anyway, Flight Simulator X is still available on Microsoft Store.