I’m pretty late in noticing this, but the Microsoft Flight Simulator is no more. Microsoft shut down ACES Studio, the internal group that developed Microsoft Flight Simulator, back in January 2009.
I think this is a shame because the Flight Simulator was one of the oldest personal computer programs still being actively developed. Although some sources (including Microsoft) state that the first version was for the IBM PC in 1982, the program actually dates back further than that.
The original version, known as A2-FS1, was created for the Apple II by Bruce Artwick and published by subLOGIC in 1980. A TRS‑80 Model I version, known as T80-FS1, soon followed also in 1980 (this was the version I first used). subLOGIC continued to develop the Apple II version and also created new versions for the TRS‑80 Color Computer, Commodore 64, Atari ST, Commodore Amiga, and others up until 1988.
In 1982, Microsoft licensed from subLOGIC a version of the Flight Simulator for the IBM PC, which they renamed the Microsoft Flight Simulator. It became enormously successful, selling 21 million copies by 1999 according to the Guinness Book of World Records. By being both very popular and very demanding on the computer hardware, the Microsoft Flight Simulator became a de-facto test of IBM PC compatibility; if a computer could run Flight Simulator, then it could be considered IBM PC compatible.
Bruce Artwick left subLOGIC in 1988 but retained rights to the Flight Simulator and continued developing it for Microsoft through his own company. In 1996, Microsoft bought the Flight Simulator outright and developed the subsequent versions internally. The final version was, released in 2006.