Humans have backwards-engineered spacecraft from ET technology and White Hats have also been given technology by Pleiadians, but stories about human spacecraft have been exaggerated to conceal Pleiadians and Galactic Federation, and their allies.
Secret spacecraft aren’t flying around trying to be seen by humans. The triangle-shaped crafts people see are Arcturian. These crafts land at military bases, and have been mistaken for secret military crafts.