X-Plane
A comprehensive, powerful flight simulator.
The developers' description:
"Welcome to the world of props, jets, single- and multi-engine airplanes, as well as gliders, helicopters and VTOLs such as the V-22 Osprey and AV8-B Harrier. X-Plane comes with subsonic and supersonic flight dynamics, sporting aircraft from the Bell 206 Jet-Ranger helicopter and Cessna 172 light plane to the supersonic Concorde and Mach-3 XB-70 Valkyrie. X-Plane comes with about 40 aircraft spanning the aviation industry (and history), and several hundred more are freely downloadable from the Internet. X-Plane scenery is world-wide, with scenery for the entire planet Earth AND MARS! (thanks to the Mars Orbiting Laser Altimeter, which mapped that planet's elevation) You can land at any of over 18,000 airports, as well as test your mettle on aircraft carriers, helipads on building tops, frigates that pitch and roll in the waves, and oil rigs... Weather is variable from clear skies and high visibility to thunderstorms with controllable wind, wind shear, turbulence, and microbursts! Rain, snow and clouds are available for an instrument flying challenge, and thermals are available for the gliders! Real weather conditions can be downloaded from the internet, allowing you to fly in the actual weather that currently exists!"
X-Plane home page