@LONGLEAVER
You're flying internationally to the UK, right? If yes, wait on ship until you're finally kicked off ship, and catch a cab and go straight to airport. There may be a queue for the cabs so you can pass a bit of time there.
You need to check in for your UK flight at least 3 hours before, and the TSA lines are long long! And boarding starts 45-60 mins before the flight's departure time. Which airline?
After TSA there are plenty of eateries and bars in the international departure area. 16:45pm is rather early therefore please do not make any plans to sightsee or get a day room as you need to be at the airport by 1-1:30pm.
We are veterans of departing from MIA airport on late afternoon international flights so we hang around in MIA airport. Walk around, eat, drink, visit the stores.