[Almdudler]

wasn't aware .png's had version updates later than 2003 (ISO/IEC 15948:2004 certificated version),
it represents a universal format used worldwide, especially on the net.

It works anyhwere else, for some reason it doesn't in AC3D.

i found out that creating .png's in Corel seems the source of the problem. Some sort of file definition must lead into a variant of png that makes it impossible
for AC3D to show it on the 3d-model.

Part of the solution (for me) is to re-open the finished .png in other paint programs, like paint.net (freeware) and save it again, let paint.net do automatic
recognition of file format settings. From now on, the textures do show in AC3D.

Another issue is that parts of the model would not show textures when running x-plane, despite everything looks fine in AC3D.
I havn't found a solution for this specific issue yet.