While I don't think they are hiding aliens and alien tech there at the base, previous history of the base, suggests that they use the base to test new aircraft tech that they don't plan on releasing information on initially. Which that does make sense, since you don't want your enemies to know what you are working on. The stretch to alien tech is a little farfetched, but I wouldn't discount it fully, as the Trump Administration had been declassifying UFO incidents from that time period.