What was the balloon filled with?
Unlike the German balloon the Hindenburg, which was filled with seven million cubic feet of highly flammable hydrogen, the massive Chinese balloon was filled with helium—and lots of it. It is estimated that it would take Party City employees six years to fill it up, longer if they had to keep stopping to wait on other customers.
How did the Pentagon conclude that it was indeed a spy balloon and not a weather balloon or something else?
Primarily through process of elimination. If the Chinese were really interested in knowing the weather over Montana, there’s an app for that. Also, since the balloon did not have either a giant Spider-Man face or the phrase “Sweet 16” printed on it, the Pentagon eliminated birthday-party décor. Therefore, it was a pretty good bet that it was either a spy balloon or a Macy’s Thanksgiving Day Parade balloon gone rogue.
