Released on July 23, 2003, this report details the causes of the failure of NASA's X-43A flight vehicle. The mishap occurred in June 2001 and was immediately followed by the organization of an investigation board, which is the source of this document. An overview of the Hyper-X Program and X-43A mission are presented, describing the components and configuration of the vehicle. The report then identifies which systems failed, when they failed, and how they affected the vehicle's operation. Much of the report's contents are fairly technical in nature, but there are nonetheless some interesting insights into the unfortunate event that are suitable for a general audience.