How the NTSB Investigates an Aviation Accident
The National Transportation Safety Board (NTSB) is the independent federal agency that, in its own words in each final report above, is "charged by Congress with investigating every civil aviation accident in the United States." Its purpose is safety. Under 49 C.F.R. § 831.4, the NTSB investigates "to determine the facts, conditions, and circumstances relating to an accident," uses those results to determine one or more probable causes, and issues safety recommendations. The same regulation says its investigations "are fact-finding proceedings with no adverse parties" and are "not conducted for the purpose of determining the rights, liabilities, or blame of any person or entity."
That is why a probable-cause statement is a safety finding, not a legal finding of fault or negligence. The two can point in the same direction or in different ones, and a court decides the second question on its own evidence.
Federal law draws that line sharply. Under 49 U.S.C. § 1154(b): "No part of a report of the Board, related to an accident or an investigation of an accident, may be admitted into evidence or used in a civil action for damages resulting from a matter mentioned in the report." The NTSB's final reports add that a separate factual report "may be admissible" under that section. For a family reading a final report, the report can explain what the NTSB concluded, but a civil case has to be proven through its own evidence.
A separate statute applies to larger accidents. An air carrier is, broadly, a business that provides air transportation to the public. Under 49 U.S.C. § 1136, after an accident in U.S. airspace involving an air carrier or foreign air carrier that results in loss of life, and for which the NTSB is the lead investigator, the NTSB's Chairman designates a director of family support services as a federal point of contact for families, and designates an independent nonprofit organization to coordinate emotional care and family support. The statute also requires the NTSB, as far as practicable, to brief families before any public briefing. For an accident involving an air carrier providing interstate or foreign air transportation, it bars unsolicited communication about a potential injury or wrongful-death action by an attorney or potential party to an injured person or a relative before the 45th day after the accident.