The Pentagon is a HUGE building. The hole made by Flight 77 looks rather small, but only because the building is so enormous. I drove by that side of the Pentagon to work every day for 9 years. It's a very solid building, too. Most of the side that was hit by the plane had just been renovated, with blast - proof windows and extra insulation installed, otherwise the damage would have been much worse.
I personally know two people who watched the plane fly into the building, one from her car and one from her apartment. I also know a woman who was an Arlington County EMT on the scene and found parts of the plane. I smelled the jet fuel burning as I drove home from DC on Sept. 11. I also am friends with the president of the Pentagon Memorial Fund, who has spent countless hours debunking these "truthers." I have seen the photos of the dead passengers found inside the rubble of the building, still strapped in their seats.
There have been lots of pictures posted on FreeRepublic and all over the Internet showing huge pieces of easily recognizable airplane debris of Flight 77.