Sublogic's FS1 Flight Simulator was the genesis of the popular Microsoft Flight Simulator series.
FS1 originated from a series of articles on computer graphics, written by Bruce Artwick throughout 1976, about flight simulation using 3-D graphics. When the editor of the magazine told Artwick that subscribers were interested in purchasing such a program, Artwick founded subLOGIC Corporation to commercialize his ideas.
The new company sold flight simulators through mail order. January 1980 saw the release of Flight Simulator (FS1) for the Apple II. subLOGIC soon followed this up with versions for other systems and from there it evolved into a long-running series of computer flight simulators.
The original simulator had black and white wireframe graphics, featured a very limited scenery consisting of 36 tiles (in a 6 by 6 pattern, which roughly equals a few hundred square kilometers), and provided a very basic simulation (with only one aircraft simulated). Despite this, it ended up being one of the most popular Apple II applications of the early eighties.
The simulator was later ported to the TRS-80 Model I, which had only rudimentary graphics capability. To squeeze the simulator into the TRS-80 limited memory and display, subLOGIC saw it necessary to drop the instrument panel. Flight Simulator for the TRS-80 therefore has the most simplistic display of all versions of flight simulator.
Later subLOGIC released updated versions of Flight Simulator for both the Apple II and TRS-80 on 5 1/4 inch diskettes. The updates included enhanced terrain, help menus and a bomb sight.
Source: Wikipedia, "History of Microsoft Flight Simulator", available under the CC-BY-SA License.