I've built a lot of airplanes. The technique I usually use is to go to the side view (or occasionally the front or top views) and draw lines to define the windows. Then you can either extrude those lines so they pass through the surface and then use Trim, or you can project the curves onto the surface and Trim. I used this technique on my Messerschmitt Libelle model which you can see a few threads down from this one. Note that when viewed from the side, the lines I had to draw were just straight lines.

I normally don't bother adding any thickness to the windows. Unless you're planning on doing an extreme close-up shot, you'll never notice the difference.

Here's a B-17 I modeled in Rhino a long time ago. For most of the windows I drew the lines in the side view. For the two front windows that the pilot and copilot look through, I switched to the front view. A few of the windows needed to be drawn in the top view.



Steve S.