Your dog is over the size limits to fly in the cabin with you. He must not only fit in the carrier, most airlines require that he be able to stand up and turn around. In addition, your carrier must go all the way under the seat in front of you, so you must be careful not to book a bulkhead seat as there will be no place to put the dog/carrier. You also cannot occupy an exit row seat when flying with a pet. Your dog must never come out of the carrier on board the airplane -- not to sit in your lap, look out the window, be walked or carried up and down the aisle or taken into the lav. You cannot carry the carrier with the dog inside into the lav and let him out in there, either. There will be a charge for your pet for every leg of the trip. Different airlines charge different amounts. If he has to ride in cargo, of course, the fees and rules are different. Look at the airlines' websites. You may know a lot of this already, so forgive me if I am insulting your intelligence, but your post is headed "first time" so I'm trying to be complete. I'm a flight attendant.