Blender Solidify Modifier

Are you going to make an interior for your aircraft or scenery object? Try using the solidify modifier to add thickness. The width can be adjusted, and as everything in this world has a width, it'll be great for everything (almost). 

Now, the main reason to use the solidify modifier is to ensure that you have double normals; that the object can be seen both outside it (exterior view), and inside it (interior view). If you have only outside normals, when you are inside the object, you will not see it! However, the solidify modifier adds double normals + thickness, so you'll see the object both inside and out!

Also, consider applying the solidify modifier to the mesh.

NB. Ensure your modifiers are applied before adding the solidify modifier. It'll make your life much easier!