Following the declassification of their project, some former employees at Area 51 finally explain what the heck was going on there: Test flights of top-secret Air Force spy aircraft called OXCART. Which looked amazingly saucer-shaped when viewed from above or below. And if commercial pilots saw one, FBI agents (no doubt wearing black) would question them and ask them to sign non-disclosure statements.
Explains a lot, doesn't it?
Except to the conspiracy theorists who'll say it's just creative misdirection . . . .