DOS

Microsoft Flight Simulator (v3.0)

Trivia

This game's package artwork and even its breathless back cover text ("Fly in formation and chase your lead plane right between the towers of the World Trade Center") seem eerily prescient given 2004 findings by the 9/11 Commission that the terrorist pilots of the hijacked planes on September 11th, 2001, trained for their operation on PC-based flight simulator software -- though presumably more recent versions of it.

During the late 80s no IBM-compatible computer was considered 100% compatible unless it could run Microsoft Flight Simulator 3.0.

According to Microsoft (http://support.microsoft.com/support/kb/articles/Q31/3/02.ASP), here is a list of changes to version 3.0 of FS (quite a lot):

     8.Version 3.00 (June 1988) 
            No copy protection.
            Can be run from hard disk.
            DOS compatible (no longer takes over the machine and forces reboot when
            finished).
            Resolution better on EGA/VGA machines.
            No longer different version for Tandy machines (Customer selects Tandy
            keyboard and/or graphics display drivers.)
            San Francisco (Bay Area) scenery added.
            Aircraft simulation enhanced.
            ADF (Automatic Direction Finder) capabilities added.
            Flight logbook and editor added.
            Computer Flight Path Display added.
            Flight Lessons.
            Demo recorder and playback system (also includes instant replay of last few
            maneuvers).
            Additional Entertainment (Crop Duster challenges accuracy skills; formation
            flying added to follow a lead plane).
            Multiple machines can be connected (direct or via modem) so players can fly
            together (and even see each other's planes on the display).
            Added Learjet.
            Editor no longer exists (pull down menus control all functionality instead).
            Flight analysis (graphs and maneuvers and/or course plotting).
            Multiple windows (can have more than one view at a time on screen). You can
            have two display windows and one map window showing location on variable
            scale map. Two display windows can be different views out of the cockpit,
            view from a spot plane, from the control tower, from a tracking observer in any
            combination.
            Clouds, thunderstorms, winds, time of day, stars can be set from the
            Environment menu (prior functionality was only a subset of this) winds and
            clouds can be set at multiple levels to simulate wind sheer and more realistic
            meteorological effects.
            Crash analysis displays a graph of the approach pattern and speed of impact.
            Smoke system added.
            Sensitivities can be adjusted for keyboard/mouse/joystick.
            More control over removal and failure of instruments.
            Multiple scenery libraries can reside on the hard disk; program automatically
            selects the right one for the coordinate setting.
            Autopilot functionality added.