Ft. Lauderdale is a well laid out airport. If it was me making such an airlines switch, I would want a two hour layover or longer. Figure 15 minutes to get off the plane, another half hour to get your luggage, and another 15 minutes to reach the Jet Blue check-in desks and re-check your bags to SXM. Then, it would be a trip through security to get to the Jet Blue departure gates. I would say another 30 minutes for that. Keep in mind that Jet Blue at FLL is located in Concourse F of Terminal 3, but this isn't like JFK or O'Hare in Chicago. It's fairly easy to get from point A to point B in Ft. Lauderdale. Hope this helps.
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