Even if it had been a balloon, it would not explain the later January
7th reports--the simultaneous sightings mentioned by Professor Hynek
in the Project "Saucer" report. This includes the thing seen at
Lockbourne Air Force Base two hours after Mantell's death.

Obviously, the saucer seen flying at 500 m.p.h. over Lockbourne Field
could not have been a balloon. Even if there had been several balloons
in this area (and there were not, by official record), they could not
have covered the courses reported. In some cases, they would have been
flying against the wind, at terrific speed.

Then what was the mysterious object? And what killed Mantell?

Both the Air Force and the Post articles speculate that Mantell
carelessly let himself black out.

Since some explanation had to be given, this might seem a good answer.
But Mantell was known for coolheaded judgment. As a wartime pilot, he
was familiar with signs of anoxia (oxygen starvation). That he knew
his tolerance for altitude is proved by his firmly declared

{p. 43}

intention to abandon the chase at 20,000 feet, since he had no oxygen
equipment.

Mantell had his altimeter to warn him. From experience, he would
recognize the first vague blurring, narrowing of vision, and other
signs of anoxia. Despite this, the "blackout" explanation was accepted
as plausible by many Americans.