Per its website, the National Transportation Safety Board (NTSB) "is an independent Federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in the other modes of transportation -- railroad, highway, marine and pipeline -- and issuing safety recommendations aimed at preventing future accidents. The Safety Board determines the probable cause of: (1) all U.S. civil aviation accidents and certain public-use aircraft accidents; (2) selected highway accidents; (3) railroad accidents involving passenger trains or any train accident that results in at least one fatality or major property damage; (4) major marine accidents and any marine accident involving a public and a nonpublic vessel; (5) pipeline accidents involving a fatality or substantial property damage; (6) releases of hazardous materials in all forms of transportation; and (7) selected transportation accidents that involve problems of a recurring nature". (http://www.ntsb.gov/)