I am currently in the process of making a plane in blender. To cut out the windows I am using the Boolean modifier, and to add thickness to the windows I used the Solidify Modifier. I would first solidify the cylinder I am using as the body of the plane and then apply the Boolean. I ONLY apply the Boolean whilst my mesh is not shaded as smooth otherwise errors occur. When I have finished using the Boolean and shade the cylinder as smooth I get a problem where there are strange cut outs in the cylinder as shown in the picture. IF anybody could help it would be greatly appreciated.
I would do two things to try and fix this. Firstly, you can try switching the order of which modifier is first.
Also, I'd try playing with the "offset" in the solidify modifier to see if that fixes it
This happened to me. It fixed its self up when I switched it from "Blender Internal Render" to "Cycles".
There was nothing wrong with the normals.