I think AA might be the only one doing it, and they charge a fee. However if you use the RCI Luggage Valet option your luggage will be checked at the pier regardless of your airline. Luggage valet costs $20 per person, and I think it covers two bags per person. They will also charge any luggage fees required by the airline. We used this in Seattle last summer and it worked well. You go to the guest relations desk and get an application. Fill it out with your airline info, etc., and the ship will print out luggage tags and boarding passes and deliver them on the last day of the cruise. In San Juan you have to carry your luggage through Customs and then go to the baggage truck. In some ports (like Seattle) the cruise line took our luggage directly from the ship to the airport. We put it outside the cabin that last night and didn't see it again until we arrived home.