YS Flight is a free flight simulator created by Dr. Soji Yamakawa. YS Flight has been in the works now for a few years and has been updated recently; now is a public release at ysflight.com. There are win32 and linux versions, it also has a multiplayer mode and a nice community.

YS Flight Simulator is a fully featured lightweight flight simulator. As well as basic functionalities, it has network feature that allows you to fly with or against your friends. You also can fly a formation leader, dogfight, intercept, attack ground, take off and land on an aircraft carrier and so on, and you can choose your airplane from more than 50 airplanes, and there are several maps as well.

• 
•