It would also be odd to film an event that you *thought* was going to bring down the aircraft...
However, filming the entire flight seems a bit weird for two reasons. The coincidence of that together with someone happening to have bomb in his undies is great. But if the guy was working with the bomber and the bomb was supposed to go off, how did he think his camera would survive the explosion and breakup of the plane?
You’ve touched on something that immediately struck me. If this isn’t just a case of something being inflated beyond what it actually was - namely, that the guy was recording “the entire flight” - then it does appear that he was expecting it to happen. If he was in on it, I’m struck by the possibility that he was a second Al Qaeda operative, sent (possibly without the knowledge of the bomber) to document the events because the bomber was given materials that were expected to malfunction, thus suggesting that what they wanted was to determine things such as how long it would take to make the device functional and detonate it, whether it would be detected, what any passenger/crew reaction would be, etc., as intel for future similar operations. Clearly, this information would be unavailable to them had the bomber succeeded.