Couple other notes:1. The only black boxes potentially destroyed were Flights 11 and 175 -- the two planes that hit the WTC. And it was presumably by the collapse of the towers, not the government.2. A lot more than just a hijackers passport survived the plane crashes (i.e. business cards, passenger licenses, misc. papers, clothing).3. All evidence and radio recordings weren't destroyed. Where do you get your information from?