http://911woodybox.blogspot.com/2011/04/pilots-strange-encounter-with-atta-at.html

http://911woodybox.blogspot.com/2010/11/was-flight-93-part-of-military-hijack.html

Excerpts:

Since 2002, when Jared Israel was the first one to point out the lame reaction of the US air defense to the hijackings (not being able to intercept leastwise one of the airliners), there's still no satisfying answer to the question for those who were responsible for the fatal delays.

...

The Headquarters and the Command Center were tracking Flight 93 as it turned around and headed toward Washington. They got the information that it was hijacked and had a bomb on board. They knew that two airliners had already been used as guided missiles - yet nobody of the leading FAA personnel bothered to follow Cleveland Center's suggestion and tell NEADS (via Dukelin) to scramble fighters. What was going on there?