The U.K.–based aircraft-charter provider PrivateFly (privatefly.com) is offering a customized weeklong Caribbean itinerary for aviation enthusiasts, or “avgeeks.” Travelers can fly to St. Martin from New York (starting at $32,000 per person) or their location of choice in a Gulfstream G650, which will nearly graze the sand of Maho Beach as it approaches the island’s airport. Day trips from St. Martin can include flights in smaller aircraft to St. Barts and Saba. Landing at the St. Barts airport requires an ext…