Area 51 was a radar testing site due to the unique properties of the salt on the ground. And they just tested a "silver shiny UFO" which was the prototype for the SR-71. And yes, this was exactly the same date when people first called radio stations and the police for UFO sightings.
The Skunkworks A-12 OXCART research project led to the final SR-71 design for the CIA's spy planes. More details on this on the CIA website for the Archangel project in the web archive [4].
[1] https://en.wikipedia.org/wiki/Lockheed_A-12
[2] https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird
[3] https://en.wikipedia.org/wiki/File:A12radartesting.jpg
[4] http://web.archive.org/web/20201112000409/https://www.cia.go...