Welcome to the forum.
I've never seen any plans to build Airstreams from, but I have seen some home built trailers styled after them, so I know it can be done.
The only suggestions I would have is to view some of the videos on line about how they are built, and that will at least give you some ideas.
Sorry I'm not more help.
"To compel a man to subsidize with his taxes the propagation of ideas which he disbelieves and abhors is sinful and tyrannical."-- Thomas Jefferson