[graniter]

I think it's pretty well accepted that the story doesn't hold up. The real question is what were they really doing. Reminds me of some teenagers that get pulled over by a cop and then tell some elaborate story about why they were speeding, who they were fleeing from, etc. Just forget their story entirely and look for evidence of what really happened.

[Steko]

The most plausible explanation I've seen is that this was a hoax/publicity stunt designed to drive a book/movie deal. Balloon boy is often brought up.