It's maxed out in the afternoon. I am sure from 6 am to noon there are plenty of slots. The issue is timing those flts to connections and having gates and ramp space at the Mainland airport. You will generally find as a example that most vacation flights to the islands never leave the US from the hubs until at least one connecting bank of flights has arrived into the hub to fill the island flight. That normally means a 9am or later departure with the flight arriving at 1pm or so. Afternoons are a madhouse at STT for that reason. There have been some STT flights where they arrive after 6 pm when it slows back down and depart early AM. Now however you have to purchase 7 hotel rooms for the crew plus transportation to and from and pay the airport to park the aircraft overnight. In addition you lose bookings because people don't want to arrive after dark and depart at dawn on vacations. The premium slots at STT are the 1 to 3 arrivals and 2 to 4 departures. It's maxed out on ramp space at those times.