Hi Helmet, and welcome to Cruise Chat.
If your departing flight is out of Ft. Lauderdale, Royal Caribbean suggests leaving no earlier than noon. If the flight is out of Miami, the official suggestion is for a flight at 12:30pm or later.
If you are willing to handle your own luggage when getting off the ship, you could leave the ship in the first group to disembark, which could be as early as 7:30am-8am. That would put you at either airport earlier, depending on when the ship is actually cleared by Customs for disembarkation, how long the line is to get off the ship, and how long it takes you to get to the airport. If there is a delay getting off the ship due to a Customs glitch, as has happened, you could be leaving the ship a lot later than anticipated.
If I fly out of Ft. Lauderdale, I don't plan flights earlier than 11:30am.