While investigating the Mantell case, I talked with several pilots and
aeronautical engineers. Several questioned that a P-51 starting a dive
from 20,000 feet would have disintegrated so thoroughly.

"From thirty thousand feet, yes," said one engineer. "If the idea was
to explain it away, I'd pick a high altitude to start from. But a
pilotless plane doesn't necessarily dive, as you know.

"It might slip off and spin, or spiral down, and a few have even
landed themselves. Also, if the plane started down from twenty
thousand, the pilot wouldn't be too far blacked out. The odds are he'd
come to when he got into thicker air--admitting he did blur out, which
is only an Air Force guess. I don't see why they're so positive
Mantell died before he hit the ground--unless they know something we
don't."

One of the pilot group put it more bluntly.

"It looks like a cover-up to me. I think Mantell did just what he said
he would--close in on the thing. I think he either collided with it,
or more likely they knocked him out of the air. They'd think he was
trying to bring them down, barging in like that."

Even if you accept the blackout answer, it still does not explain what
Mantell was chasing. it is possible that, excited by the huge,
mysterious object, he recklessly climbed beyond the danger level,
though such an act was completely at odds with his character.

But the identity of the thing remains--officially--a mystery. If it