Johnson publicly announced the SR-71 in 1964, so the plane wasn’t top secret at the time (in the mid 1970s). New York Times story about the announcement: https

Johnson publicly announced the SR-71 in 1964, so the plane wasn’t top secret at the time (in the mid 1970s). New York Times story about the announcement: https://archive.md/oFO9J https://archive.md/oFO9J