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.