Forty years on, proof

This splendid book has one fascinating (well, to Rico, anyway) tidbit in it: the very existence of the 6513th Flight Test Squadron, the 'Red Hats', based out of various obscure Air Force bases in Nevada.
The job of the 6513th (later the 413th) was to evaluate various Soviet aircraft that ended up (through defections, or Israeli captures) in American hands.
Why is that of interest to Rico? Well, because back in 1968 or 1969, Rico and some of his buddies were camping up in a little valley (the Usal) in Northern California. One day, whilst clambering around on the cliffs above the Pacific, they noted an aircraft coming, very rapidly, in-bound off the ocean. It thundered ashore below the top of the cliffs, flying up the valley of the Usal. It was, or appeared to be, a Russian aircraft in naval colors. It was followed ten or fifteen seconds later by one pair, then another, of standard US Navy airplanes, also flying low and going hell-bent-for-leather in the wake of the Russian plane.
We all figured it was the start of World War Three and, what with the bad radio reception in the old VW van we were driving, weren't sure what was happening until we got back to civilization. No war, but no answers either.
Rico asked a buddy of his, years later, who was still in the Navy Reserves; he asked someone he knew, but the only answer given was "Ah, so they saw them, did they?"
Now, at least, we know who 'them' were...