We cruised on the Celebrity Zenith from Ft. Lauderdale on March 13, 1993. Airports throughout much of the Midwest and East were closed by The Storm of the Century! The captain delayed our departure 4 or 5 hours to give passengers a chance to arrive, but finally left with approximately a fourth of the passengers missing. We had flown to Florida two days earlier to take our children to stay with my wife's parents, so we didn't have a problem. But two of our tablemates joined the cruise two days later in Jamaica, with horror stories to tell!
Based on this experience, we flew down to Florida a day early for our Disney Magic cruise a few months ago. It was a great way to start the vacation. We spent the afternoon at the resort pool. We had a good dinner at Bahama Breeze near WDW. And the next morning, we only had to drive to the port and return our Hertz car in Cocoa Beach.
Even if someone could guarantee that our flight wouldn't be cancelled or delayed, I wouldn't want to fly on the morning of the cruise. To take a 7:00 a.m. flight from O'Hare, we would have to leave out house at between 4:30 and 5:00 a.m. -- given the need to be at the airport at least 90 minutes before the flight and to make it to the front of the check-in line to check bags at least an hour before the flight. Who wants to be exhausted when you board the ship?