Staff Report of the 9/11 Commission on Terrorist Attacks upon the United States, August 26, 2004 [open pdf - 10MB]
This staff report is divided into two parts. Part one outlines the chronology of events of the four 9/11 terrorist flights. Part two analyzes civil aviation security and its connection to the 9/11 attacks.
U.S. National Archives & Records Administration: http://www.archives.gov/