I've been on AA flights, including one to Aruba many years ago, where the MIA departure delay was due to waiting for a new crew to arrive because the current crew reached the maximum # of flight hours for whatever period they use to track these things. I've also been delayed waiting for a plane to arrive & then take us on to MoBay. One time, based on the airport the flight was arriving from, they actually could have made the trip to Tampa twice in the time we were delayed waiting on the plane. Sheesh. I know stuff happens but it NOT happening is the exception on AA. I wish that was an exaggeration but it's not. Boy, I really miss the days of NWA's non-stop flight from Tampa to MoBay.
BTW... even though I've only flown through Dallas-Ft. Worth once & it was on AA (a non-Jamaica trip). No problems, everything on time. Nice airport, too. Still keep checking on your times though. They can still change.