Also, in late 50's, early 60's, imagine seeing an SR-71 flying at any speed or
angle. That would be something incomprehensible to 3/4 of Americans or more. Or seeing the outline of it from below, and traveling Mach 2, it's not something you'd think "plane." In every regard, it's so far out, I've always thought it probably accounts for a sig. amount UFO sightings for the time.
BTW, I've always been a big time sceptic of UFO's. We know how terrible human beings are as eyewitnesses, according to many different research sources done on the matter. I've been pretty amazed by the content on History Channels "Unidentified: Inside America's UFO Investigation." There's definitely more stuff on the matter from military and gov. sources than I ever realized. Interesting show, if you have any interest yourself. History Channel has become a total joke re; real history content, and even for a reality type show, this one's worth checking out.