In other words it could have been caused by anything, even a missile. Moreover, then Secretary of Defense, Donald Rumsfeld is on record as implying as much in the interview below from Parade magazine, published shortly after 9/11.

Of course, he may have just fumbled his words but Rumsfeld has a habit of doing this; inadvertantly saying what really happened, such as when he let slip that United Airlines Flight 93 was shot down.

Moreover that mouthpiece for New World Order propaganda, the BBC, announced that:

“The release of new video pictures of the Pentagon being attacked on 9/11 will not quell the endless claims in the world of conspiracy theorists that a missile or military aircraft hit the building instead.” http://news.bbc.co.uk/1/hi/world/americas/4990686.stm

Two things emerge from this:

First the powers that be are growing seriously worried about the questions being asked about 911. The fact that the BBC is now being used to undermine and question “conspiracy theorists” is a sure sign that the Illuminati are concerned.

Just as the British Broadcasting Corporation repeatedly reported on Saddam Hussein’s WMD’s prior to the invasion of Iraq – and thereby provided its justification – until it was found that there were no Iraqi WMD’s and had never been. When all such BBC reports suddenly stopped.

So, instead of examining what researchers are saying, the BBC now paints them as "conspiracy theorists" without any further investigation.

You will also note that the pictures provided by the BBC are small and show far less than those below. Another example of the BBC's reporting being used to divert attention and conceal rather than reveal.

So unless the Internet highlights it, don't expect the BBC to probe or even question Rumsfeld's gaffe/admission.

Donald Rumsfeld on the “Missile” that Hit the Pentagon
The 7th Fire.com

Secretary of Defense Donald Rumsfeld was interviewed on 12 October 2001 by Lyric Wallwork Winik (yes, that's her real name), a columnist for Parade, the magazine that comes in many Sunday newspapers across the US. Although Parade is one of the most mainstream magazines imaginable (think People meets the Saturday Evening Post), Winik blindsided Rumsfeld with a question that few reporters/interviewers have the guts to ask:

"This is a question that's been asked by many Americans, but especially by the widows of September 11th. How were we so asleep at the switch? How did a war targeting civilians arrive on our homeland with seemingly no warning?"

Rumsfeld is apparently shaken by this young reporter's forthrightness. First, he admits what few else dare:

"There were lots of warnings."

Immediately after this sentence, though, the Secretary starts to qualify it. He subtly plays the "we didn't connect the dots" card:

"The intelligence information that we get, it sometimes runs into the hundreds of alerts or pieces of intelligence a week. One looks at the worldwide, it's thousands. And the task is to sort through it and see what you can find."

Although he doesn't directly say it, it would seem that Rumsfeld is insinuating that the poor, understaffed, shoestring intelligence and defense establishments can't put together intelligence in a timely manner.

Now things get really bizarre. After admitting that there were plenty of warnings, he says it was up to the FBI and especially state and local law enforcement to deal with the imminent terrorist attack:

"And as you find things, the law enforcement officials who have the responsibility to deal with that type of thing -- the FBI at the federal level, and although it is not, it's an investigative service as opposed to a police force, it's not a federal police force, as you know. But the state and local law enforcement officials have the responsibility for dealing with those kinds of issues."

To sum up Rumsfeld's explanation: 1) The warnings were there; 2) the Defense Department and the intelligence community couldn't figure them out; but anyway 3) it was up to the FBI, state law enforcement, and local police to uncover and prevent the worst terrorist attack in US history.

And here's something to kick around. Still answering this question, Rumsfeld goes on to make a strange statement:

"It is a truth that a terrorist can attack any time, any place, using any technique and it's physically impossible to defend at every time and every place against every conceivable technique. Here we're talking about plastic knives and using an American Airlines flight filled with our citizens, and the missile to damage this building and similar (inaudible) that damaged the World Trade Center. The only way to deal with this problem is by taking the battle to the terrorists, wherever they are, and dealing with them."

"Missile"? What missile would that be? Did he let something slip? Or was this just a gaffe? A bad choice of words? A transcription error? Until we know for sure, it deserves scrutiny.

The article based on this interesting interview was "We Have to Defend Our Way of Life" by Lyric Wallwork Winik in Parade, 18 Nov 2001. The only part of the above exchange to be included is this:

To Rumsfeld, the Sept. 11 attacks did not come as a complete surprise. "There were lots of warnings," he says bluntly.

"The only way to deal with this problem," he continues, "is by taking the battle to the terrorists and dealing with them."

Now, it is pretty bold for Parade to quote him about the warnings. Of course, the magazine then skips Rumsfeld's subsequent shifting of blame and use of the word "missile," jumping right to the innocuous final sentence of the exchange.
Source: www.the7thfire.com/Politics%20and%20History/Missile-Not-Flight-77.html

Full text of interview archived here
www.the7thfire.com/Politics%20and%20History/t11182001_t1012pm.html

Photos from:
http://911research.wtc7.net/pentagon/evidence/videos/uncropped.html

Now contrast the images above with this admitted fake video and ask yourself: where is American Airlines Flight 77?