I've never flown an animal anywhere, so I'm not sure about this, bit I was thinking- it may not be too badly of an idea to give him a mild tranquilizer while he is on such a long trip, to calm his nerves. I don't know anything about tranquilizers or if they are safe, but it's something I'd consider asking my vet about. I'm not sure if this is something that's been mentioned yet. I'm sure others here will know more about it than I do (after all I know nothing at all about it).