Wow!  I was looking for 3ds Tutorials when I came across this page.  The files are all Autocad or.prj files, but can easily be imported into Gmax.  Plus they are all free!  I would recommend you do not try to call them your own, but give credit to the original site.  Some of these are not very detailed, but some are really nice.

Go get 'em!

http://www.3dcafe.com/asp/aircraft.asp

I've downloaded a few. 

In most cases, you still need to cut out control surfaces, etc., but as you say, the bulk of the project is done.