911Truth.org has a brief new article about the "Military Exercises" that preceeded, and took place on, 9/11. To give it some context, I'll post some links to some other, older articles, as well.

Exclusive Report: Did Military Exercises Facilitate the 9/11 Pentagon Attack? - July 2006

...We can see that Pentagon training exercises prior to 9/11 routinely involved the simulated crashing of an aircraft into the building. But might another such exercise have been scheduled for the morning of 9/11? There are various pieces of evidence indicating this may have been the case. Although the existence of such an exercise has never been stated explicitly, this might be because the exercise was declared classified....

...In addition, a December 9, 2001 Toronto Star article reprinted here, stated that "Operation Northern Vigilance is called off. Any simulated information, what's known as an 'inject,' is purged from the screens". This indicates that there were false radar blips inserted onto air traffic controllers' screens as part of the war game exercises...

...Why did an internal FAA memo claim, that at around 9:18 AM, two cockpit members had been stabbed and at around 9:20 AM, one of their passengers, Daniel Lewin (Seat 9B), former member of Israel's elite anti-terror commando "Sayeret Matkal" had been shot? Was Lewin maybe involved in a passive observation or active participation of this drill?...

...Representative Cynthia McKinney (D-Altanta) attempted to bring some attention to the 9/11 war games during the House Hearing on FY06 Department of Defense Budget, on March 11th, 2005. She questioned Secretary of Defense, Donald Rumsfeld and Chairman of the Joint Chief of Staff, Richard Myers about the four war games that took place on September 11th. Myers responded to the question with very ambiguous explanations. He claimed that war gaming was being held by several different departments and it was not NORADs overall responsibility to respond to the attacks, but the FAA’s. Nonetheless, he felt the gaming actually provided “an easy transition from an exercise into a real world situation” and contributed to a quick response. Myers failed to comment on McKinney’s question of who was actually in charge of managing the war games on 9/11 (Kane 3/1/2005)...