I will be flying in and out of the Cyril E. King airport on St. Thomas in December, coming from the US. I have read conflicting reports as to when you should arrive at the airport on St. Thomas to return to the U.S.. I've read 90 minutes (American Airlines site) to 3 hours before your departure time. Does anyone have an insight on this? 3 hours is awfully early and a long time to hang out in a very small waiting area!!! Thanks!

Hi There. I live in the Virgin Islands. I would say that minimum 90 minutes before arrival, especially if you have checked bags. For 2 reasons:
One of them is: 90 minutes is often the cut off time that checked bags have to be received by the airline in order for you to board your flight. I know this first hand when I missed the 90 minute cut off for American Airlines to check in my large luggage. Since I was just under the 90 minutes, the airline would not accept my checked luggage. So I wound up having to miss my flight because I obviously couldn't abandon my checked luggage at the airport.
Another reason is because as you mentioned the small waiting area... it's a pretty small airport servicing many passengers per day. It can be very busy and overwhelming at the long checked bag lines. I have learned not to travel light, not check bags and skip that line. Customs lines can also be long.
However, as long as I get there at least 2 hours before the scheduled departure time, I have been fine.
If you are coming for the first time - don't pack so much. You don't need much in the islands. I can't believe the amount of stuff I see people dragging with them. 1 pair of flip flops. 1 pair of walking shoes. 90% casual, light clothing.

Thank you for your thorough reply, I appreciate it!