If you have a through ticket to the BVI, can't the airline ask for your test results? I have seen a lot of itineraries going through STT connecting to the BVI on Cape Air.
Somewhere along the path, someone is going to ask so be prepared to show it. Lots of confusion out there among the gate agents about rules.
When I flew thru SJU at the end of September, I was the first person to let the Cape Air ticket counter agent know that the gateway requirement was going away in 2 days and they would have to start confirming vaccination status.
