After a cruise ending in FLL, I'll be taking a shuttle to MIA to fly home on UA. The problem is arriving at MIA before noon for a 5:45 p.m. flight with a suitcase that must be checked. I know at most airports you can't check in earlier than four hours before a flight, but does MIA make an exception due to cruises?

I don't mind hanging out in the CO or US lounge, but I don't want to spend three hours with my luggage outside check-in. And I don't want to spend money on an overpriced post-cruise tour. Renting a car for the day is not an option.