Fighter Squadron: Screaming Demons over Europe is a WWII flight simulator. In
Fighter Squadron you can fly a selection of ten different US, British and
German fighters and bombers in a series of 30 missions over Dover, the heart
of Germany, or North Africa.You can play the missions for either side, man any
of the aircraft, as well as change positions inside the bombers to man the
guns and bombsight.

It also allows the users to add their own planes, vehicles and missions via a
text-based plug-in format called OpenPlane. Every part of the aircraft is
individually listed in its OpenPlane file and can be edited – you can change
the power of the engines for instance, or the distance the various gun turrets
can traverse.