I read the Wikipedia entry on it. A mystery, not a mystery about flying saucers and aliens, but how the story originated and why.
Similar to the Lonnie Zamora case which is the most intriguing UFO incident ever. That man saw what he told everybody he saw, he was a police officer, wasn't drunk, took a lie detector i believe and passed - he saw some kind of odd vehicle and two individuals outside it, then it lifted off and flew away. I read a long, as in years long, thread on some website/blog where people who had first hand knowledge of the Zamora incident including some of the engineering students at the college nearby who were thought to be responsible for making the craft as some kind of elaborate prank. Impossible to know, people who claimed they knew first hand it was a prank, no way of knowing if they're telling the truth. Same for everybody else involved.
The most likely explanation is Zamora came upon some military/NASA thing he nor anybody else was supposed to see. Some have speculated the craft may have been a very early prototype of the lunar landing module that would be used in the Apollo moon missions.
I've heard of the Zamora case, but am not knowledgeable about it. I think that's the one that occurred somewhere in New Mexico.
I am by no means a "true believer". For starters, I've never seen anything I would consider abnormal in the sky. Not saying I could identify everything with precision, but nothing ever dumbfounded or perplexed me enough to consider it much. If you think about it, belief is quite a commitment. However, I'm open to the possibility of high strangeness being witnessed by others. Can't say spaceman piloted aircraft would be my starting point, but cases like Aerial School, Pascagoula, Devil's Den, and the Travis Walton case give one pause.