This is the cover of a report on the Teledyne Ryan Aeronautical “Navy Mini-Drone (STARS),” otherwise known as the Manta Ray. It was a fiberglass remote-controlled drone; STARS stood for “Ship Tactical Airborne RPV” (for “Remotely Piloted Vehicle”).
The image came from the Robert Hersey Collection hosted by the San Diego Air and Space Museum on Flickr; they’ve also got some photos of the vehicles themselves, including some next to humans for scale. The Manta Ray was not very large, as aircraft go — barely as big as its namesake sea creature, really — and was powered by a 25 h.p. McCulloch chainsaw engine, from what I can now read on the internet. Back in the day, this was a secret program, and only three of these were ever built… as far as we know.
Of course, UAVs are a much more sophisticated and more widely known part of military technology nowadays, but these guys were a lot closer to UFOs at the time. They were built to have a low radar profile and to able to be recovered by a large net — no fancy landing maneuvers. And they did move in a peculiar way… there is video we can see now.