How many times did we see the video clips of the planes hitting the World Trade Centre? It was repeated almost like a loop on every channel until the horror of the event was permanently burned into our memories.
Yet what can be said of the plane crash at the Pentagon - we heard about it soon enough, but very few images were forthcoming on the day, and the bulk of what we saw afterwards were still photos of the collapsed portion of the pentagon and a few pictures of fire-fighters attempting to extinguish the blaze. No sign of any video recordings, very few witness reports and definitely nothing to show us the event as it happened.
Have a look at the following two links - it appears the Pentagon's security cameras failed to capture the crash on CCTV, yet a nearby hotel and a gas station had security cameras which DID manage to capture the whole event. Pretty poor security at the Pentagon - its just a wonder that no-one else is trying to attack the world's only superpower if the security cameras on their military command centre can't manage to film a plane crashing into the building. The FBI came and confiscated all the tapes without even having the common courtesy to give them to CNN so we could see them 56 times a day. Were they worried that we might see pieces of paper with state secrets on them flying out of the building? What exactly are they worried we might see?