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As an example of the site's important work, here is a recently added 9/11 Timeline entry:

After September 11, 2001: Unlike Previous Incidents, NTSB Does Not Investigate 9/11 Plane Crashes
In the weeks following 9/11, the National Transportation Safety Board (NTSB) assists the FBI in its response to the attacks. Over 60 NTSB employees work at the scenes of the crashes--the Pentagon, Pennsylvania, and New York--and at the board's headquarters in Washington, DC, helping to identify aircraft parts, searching for and analyzing the flight recorders, and assisting the victims' families. [National Transportation Safety Board, 9/13/2001; US Congress. Senate. Committee on Commerce, 6/25/2002] However, unusually, none of the four planes that crashed are the subject of formal NTSB investigations. According to Vern Grose, a highly respected air disaster analyst and former NTSB member, "First of all, after any aircraft crash, the NTSB [normally] launches what they call a 'go team' within two hours and that go team will have up to twelve people on it. Specialists in airframe, in engines, in electronics, in human factors. And these folks all go to the scene—they isolate the scene. From that point on, it's the NTSB's responsibility." But with the crashes on 9/11, Grose says, "it's my understanding that it did not occur exactly like that. They may have launched an NTSB crew, but it never took the same course a normal investigation would have." [Lappe and Marshall, 2004, pp. 40-41] The NTSB says that, because the four crashes were "criminal acts," the FBI is consequently the "lead investigative agency." [National Transportation Safety Board, 9/13/2001] Therefore, the NTSB will later state that it "did not determine the probable cause" of any of the four crashes, "and does not plan to issue a report or open a public docket." [National Transportation Safety Board, 3/7/2006; National Transportation Safety Board, 3/7/2006; National Transportation Safety Board, 3/7/2006; National Transportation Safety Board, 3/7/2006] However, even under these circumstances, Grose calls the lack of NTSB investigation "unacceptable." He says, "Though the NTSB statute states the leadership of the investigation will defer to the FBI, the NTSB has still completed formal investigations into crashes deemed criminal acts." It previously did so, for example, in the case of EgyptAir Flight 990, in which a pilot crashed a plane in an apparent suicide attempt (see October 31, 1999). [Lappe and Marshall, 2004, pp. 41] The Pittsburgh Post-Gazette complains about the unconventional investigative process, specifically in relation to Flight 93, which crashed in Pennsylvania. It says that, while the NTSB is "a small government agency whose procedures are fairly open," with the FBI instead handling the investigation, "everything, even the most minute details, are being kept under strict lock and key." [Pittsburgh Post-Gazette, 11/4/2001] As well as the lack of an NTSB investigation, attempts at conducting a precise grid search of the Flight 93 crash site will be overruled by the FBI (see September 16, 2001). [Longman, 2002, pp. 262]
http://www.cooperativeresearch.org/context.jsp?item=a091101nontsbinvestigation&scale=0