I ssw Hynek give a lecture on UFOs, this was late in the 1970s, and probably came about due to “Close Encounters of the Third Kind” (one of the worst movies ever made, IMHO, by the way). I remain impressed by his thoughtful and limited claims, and well-structured avenues for study.
BTW: In Hynek's book, "The UFO Experience: A Scientific Inquiry", there were 4 chapters that (IMO) were the better parts, Close encounters of the first kind, Close encounters of the second kind, Close encounters of the third kind, and Close encounters of the forth kind..
This is where the title of the movie came from...