When I was in tech school in the U.S. Air Force in late 1976 one of the instructors told a story of an incident that supposedly occurred in Washington State around the time of the first "oil crisis" c. 1973.
There was an AC&W radar site in Washington State, on the coast, near an area with a large number of oil storage facilities. The site began to get telephone calls reporting a large aircraft flying low in the area with no running lights. The site could see nothing on the radar. Some of the guys went outside to see if they could see anything, which they could not. Suddenly, a Tu-16 flew, at very low level, directly over the dome, heading out to sea. Finally, the target was observed by the radar about 40 miles out, climbing away. By then it was too late for an interception.
I don't know if this really happened, but it sounds plausible and was a good story.