One option is to make your 1st flight. Then, say when you are MIA, call the RTW desk to make the routing change. AA has a city ticket office at American Airlines Arena which is at Biscayne Blvd. & NE 8th street downtown. Only 4-5 miles from the airport should you need to have the ticket re-written or such; not sure what policy is with new e-tickets, I'm still on a paper ticket for current RTW!