Delta is not and I don’t believe any airline is checking Covid tests. However, the National Guard is in charge of checking for Covid tests once you land You are suppose to fill out the USVI portal showing your Covid test. If you didn’t file out the portal they just have you fill out a paper version and show your tests results.
Unless Delta is flying you to Beef Island somehow, they have no obligation to check you. Either the ferry or airline bringing you to the BVI is required to confirm you have been tested and vaccinated.
