BountyKilla
The DCA (Directorate of Civil Aviation) resides on Antigua and is responsible for air traffic on the former British islands, now known as Overseas Territories if still loosely governed by the UK through Governors although they have their own local Chief Minister or independent islands such as Antigua/Barbuda, St. Kitts/Nevis, British Virgin Islands, St. Lucia. All have chosen/been forced to be guided by the DCA for the sake of simplicity.
Sint Maarten (one half of the island, the northern part Saint Martin being French territory governed directly from Paris as are Guadeloupe, Martinique, St. Barthelemy + some more) belongs to the Netherlands Antilles (SXM, Curacao, Aruba, Bonaire, Statia aka St. Eustacius and Saba)which are in effect very similar to the British Overseas Territories and have their own, NA CAA.
As all the islands depend heavily on air transport cooperation is usually easy. But all have different licences. OECS DCA uses Air Navigation Order (ANO) Overseas Territories amended 2000ish.
Don't forget the US islands.