Microsoft Flight Simulator X (known in the Flight Simulator community also as simply FSX, of which the X is pronounce ten, as in the Roman numeral) is the latest version of Microsoft Flight Simulator after Flight Simulator 2004. It includes a graphics engine upgrade as well as compatibility with Windows Vista, having been hailed by Microsoft as the most important technological milestone in the series to date. It is the first version in the flight simulator series to be released on DVD-ROM.