OK, so I'm trying to create a time line... feel free to correct me on anything or point out some other possibilities.
Leave London, on the 14th
Flight Schedule Dec 14th Heathrow London to Kingston Jamaica:
9:45am 5:05pm KIN BA 0207 / DL 8864* 744/320 MIA 2:35 hrs.
9:45am 5:05pm KIN BA 0207 / JM 0024 744/320 MIA 2:35 hrs.
9:45am 5:09pm KIN BA 0207 / AA 1733 744/738 MIA 2:40 hrs.
9:45am 5:09pm KIN BA 0207 / 5195* 744/738 MIA 2:40 hrs.
10:20am 5:05pm KIN AA 0057 / DL 8864* 777/320 MIA 1:45 hrs.
10:20am 5:05pm KIN AA 0057 / JM 0024 777/320 MIA 1:45 hrs.
10:20am 5:09pm KIN AA 0057 / 1733 777/738 MIA 1:50 hrs.
So, the earliest any team can arrive in Jamaica is 5 ish, leaving only 30 minutes of daylight from touchdown, so tasks done on the 15th... We know they're all together at least at some point of this, doing daylight tasks in Jamaica.
Complete Task sometime on the 15th, maybe even before noon, so they can leave Jamaica that same day. They'd have to do this, because from the flight searches, I see no 16th or 17th flights out of Jamaica to San Juan, unless they were to have the teams do something other than fly. BUT now that we see U&J at the Jamaica airport, they must have to fly... so the 15th it is...unless there is some little know charter airline running that flight, or some other connection not shown on searches.
Flight Schedule Dec 15th Kingston Jamaica to San Juan Puerto Rico:
12:35pm KIN 6:24pm SJU BW 0415 / AA 5171* 738/AT7 SXM 1:35 hrs. (anyone know what airline BW is?)
12:35pm KIN 6:58pm SJU BW 0415 / AA 5165* 738/AT7 SXM 2:10 hrs.
So, they get to Puerto Rico at 6:24 pm on the 15th, again no daylight for tasks, tasks done on the am of the 16th-complete afternoon of the 16th.
IF, there's going to be a mugging, there must be one after the PR tasks. It couldn't be in Jamaica, because there are no flights on the 16th or 17th heading to PR. The only way for the teams to be leaving Puerto Rico on the 18th, is if they hold off the pit stop till Puerto Rico. (unless of course as noted above, there are flights that are not showing up in searches)
Since this is the last leg of the race, teams have a 36 hour pit stop, and leave PR early AM on the 18th for Miami.
OK, so I'm trying to see how R&A could get such a big lead. Let's say they rock their tasks in PR. Awesomely rock em, and are done by 10 am. Then the rest of the teams aren't done until, let's say even 6pm. R&A don't set out till 10pm, too late for an immediate flight out, and the other teams get to leave at 6:00 am, with some time to catch the earliest flight out.
OR, another scenario, since we see Joyce breaking down in the Jamaica airport, is that they miss those two flights to San Juan. They figure their are majorly screwed since there are no flights on the 16th and 17th... but they find an alternate way to get there... they must, because they are seen in PR on the 18th.
The biggest chance for a R&A lead, is that R&A ARE the only ones who make that 12:35 flight to San Juan. R&A and R&K have to find alternate transport, and are over a day behind. They'd have to be, because a 6:24 pm arriving flight for R&A, leaves a lot of room for teams to catch up, when they have to wait till the next day to start tasks. Unless they have nighttime tasks in PR of course.