Hello geg - yes, that may another and perhaps preferable way of doing it. The Swiss aircraft could be loaded in the main folder with the "S" rather than "P" prefix (also planes.dat and flt files).
What I am probably then going to have to do is have an overall "!940" manager. That will detect which module is currently loaded and if neccessary select the module being used - Dunkirk - Swiss - Alpes etc, and then make any aircraft changes. You then enter the Manager for the module. Don't want to make it too complicated
The separate exe for each module would then call the different screens, and could also manage differently named savedata and even music files.
Speech is another thing I need to think about. The Swiss had German French and the odd Italian speaking squad. Perhaps I could swap speech when the squad was chosen.