Back in the 70s I was at Camp Pendleton and one particular day just happened to look up. Typically beautiful Southern California day with a pale blue cloudless sky.
There, hanging perfectly still at a 30 degree angle, was something that looked like a "H" lying on its side, with the upper leg being a tad shorter and having one fat and two thin crosspieces. It looked like somebody took an India Ink pen and drew it there. The hair on my neck stood straight up.
Then as I watched, it slowly changed to a silvery color and began moving. In a few seconds I recognized it as a twin engine, multi-rudder aircraft that had a radar dome on top, which gave it that horizontal "H" double-bar silhouette.
(Length=500 HTML no workeee with this one)
I must have caught it as it was making a turn, looking head on, and for a second, a trick of light made it look motionless and jet black. After that, I could well sympathize with someone freaking out after seeing a real UFO. One Helluva experience.