We have taken 2 cruises with Carnival and have flown in on the day of the cruise. We
book our own airfare and have not had a problem as of yet. A few suggestions: Book
the earliest flight you can with the least amount of connecitons. This will allow for
delays and less chance for misplaced baggage. On our first cruise, our flight (non-stop)
was delayed 2 hours and we still made it to the ship 2 hours before sailing. As long
as you can be at the port at least 2 hours before sailing, you should be okay.
P.S We care cruising on RCCL in March, flying in the same day.....