Having flown to many cruises (non-Disney) over the years, I would definitely advise flying in at least a day early. When we first started cruising, we flew in the day of, and then spent that first day on the ship resting up from our trip down - and that was way before all the security procedures. Then we started flying down at least a day early - getting a good nights sleep and then boarding the ship rested and ready to enjoy our first night.