https://www.yojoe.com/vehicles/86/nightraven/
There were accurate SR-71 scale model kits by Monogram and Revell that I was putting together with Testor's glue in elementary school. It was not classified for 40 years. From 1959 to 1979 would indicate 20 years, if that.
https://en.wikipedia.org/wiki/Monogram_(company)
I was a small child when I learned about Guinness world records, and first discovered the SR-71 while writing a book report. It was understood that the blackbird had established records of mach 3 in the late 1960's. They even used to have an exhibit of Guinness records in the lobby of The Empire State Building in Manhattan that included this record.
The Guinness record states 1968, and that was in print in the early 1980's. You can probably buy old, used copies of Guinness World Records editions, which prove this.
https://www.amazon.com/Guiness-Book-World-Records-1980/dp/08...
The 1988 edition had a newsprint/paperback quality photo of the plane:
https://www.amazon.com/Guinness-Worlds-Records-Giant-Revised...
Parts of the program were obviously classified, but the aircraft was known to exist and was photographed by the press, unlike the F-117 and B-2, which had not emerged into public until the 1990's.
How terrifying. To think that we could have been living in this world for 10 years now and not even realize it.
Remember the SR71 spy plane was classified for 40 years and when it was finally acknowledged after all that time it was still the fastest airplane ever created.
Military technology tends to have a guiding effect to regular technology. I wouldn't be surprised to learn that war has been guided in some capacity by AI for quite some time.