I have used tranquilizers transporting my dogs on planes. Otherwise not so much. However, with cats you have to keep in mind that they can be more attached to their home than their owners. So if you are going to move such an animal, you need to mitigate the psychological anxiety of being separated from the only environment that they have ever known. That can generally mean keeping them somewhat sedated until they get accustomed to the new environment. He will probably hide for a long time.