Bring along any medicines your cat will need to stay healthy and calm. That includes all of the pills he normally would take for the amount of days you'll be away (plus a few extra pills in case you can't get back home as early as planned), flea and tick medicine if he's due, and an anti-diarrheal medicine to help avoid unpleasant accidents (ask your vet for a recommendation). Don't bring along any new medications that your cat hasn't taken before. You don't want to risk a reaction while you're traveling.
Some people like to sedate their cat on long trips, but experts don't recommend giving cats tranquilizers, because they can raise blood pressure and interfere with body temperature regulation. An animal that's been sedated can lose its equilibrium, making it hard to stay balanced. If the carrier is being moved or is shaking during a turbulent flight, unsteady balance will increase your cat's risk of injury.