A[IMG]http://cakecentral.com/content/type/61/id/3224674/width/200/height/400[/IMG]

How would I go about making this cake 3D?

If I were you, I would just carve out the main shape, cover it in fondant, and then decorate it. You can do the wings out of something inedible and cover them with fondant too. Here is a truck that I carved and then covered in fondant.

Thanks that was what I was thinking. I was just hoping someone had some kind of simple way for me to do it. I have made cars out of RKT. But the customer wants the whole plane cake. So I guess I will just hope for the best!!

AI'd make the wings with foam core, everything else could be cake. The supports, you can work those in where the wheels would be, so there wouldn't be anything out of place.