So the trick for all illegals is to not have a valid passport, and thus they'll have to stay in the US because the airlines won't put them on a plane?
Sorry for the snark, but that's how I read this thread. Tell the guy to go to his closest consulate and get a new passport JUST TO MAKE THINGS EASY. However, even if he doesn't, if he's returning to his home country, he most likely doesn't need a valid passport to get in, and that getting in is all the airline cares about.