I wonder if it is a coincidence that this is the second time there has been external pressure to remove a paper from the Journal of 9/11 Studies whose focus was "Other" planes in the air at the time of the attacks.

from a friend on another board:

Here's video of the plane:

http://www.youtube.com/watch?v=gGSwve_BU9I&mode=related&search=

Here's a photograph of it from the USAF website:

http://www.af.mil/factsheets/factsheet_media.asp?fsID=92

Edit: This, too.

Lt. Col. Steve O'Brien started his day at the controls of a Minnesota National Guard C-130 cargo plane. He and his crew were heading back to the Twin Cities after moving military supplies around the Caribbean. About 9:30 a.m., O'Brien throttled the lumbering plane down a runway at Andrews Air Force Base, just southeast of the District of Columbia.

"When we took off, we headed north and west and had a beautiful view of the Mall," he said. "I noticed this airplane up and to the left of us, at 10 o'clock. He was descending to our altitude, four miles away or so. That's awful close, so I was surprised he wasn't calling out to us.

"It was like coming up to an intersection. When air traffic control asked me if we had him in sight, I told him that was an understatement - by then, he had pretty much filled our windscreen. Then he made a pretty aggressive turn so he was moving right in front of us, a mile and a half, two miles away. I said we had him in sight, then the controller asked me what kind of plane it was.

"That caught us up, because normally they have all that information. The controller didn't seem to know anything."

O'Brien reported that the plane was either a 757 or 767 and its silver fuselage meant it was probably an American Airlines jet. "They told us to turn and follow that aircraft - in 20-plus years of flying, I've never been asked to do something like that. With all of the East Coast haze, I had a hard time picking him out.

"The next thing I saw was the fireball. It was huge. I told Washington the airplane has impacted the ground. Shook everyone up pretty good. I told them the approximate location was close to the Potomac. I figured he'd had some in-flight emergency and was trying to get back on the ground to Washington National. Suddenly, I could see the outline of the Pentagon. It was horrible. I told Washington this thing has impacted the west side of the Pentagon."

O'Brien asked the controller whether he should set up a low orbit around the building but was told to get out of the area as quickly as possible. "I took the plane once through the plume of smoke and thought if this was a terrorist attack, it probably wasn't a good idea to be flying through that plume."

He flew west, not exactly sure where he was supposed to land. Somewhere over western Pennsylvania, O'Brien looked down at a blackened, smoldering field. "I hoped it was just a tire fire or something, but when I checked with Cleveland center, he told me he'd just lost a guy off the scope pretty close to where we saw it. By then, we were able to patch in AM radio, so we heard about all the planes. It was like a domino effect - a really bad day for airplanes."