In 1983 , he was appointed by President Ronald Reagan to the National Transportation Safety Board , where he pioneered the concept of multiple causation of accidents . Following his appointment to the NTSB , he was appointed to serve as a member of the National Highway Safety Advisory Committee . In 1997 , Vice President Al Gore requested his assistance and expertise on the White House Commission on Aviation Safety and Security . Following the September 11 attacks on the World Trade Center and the crash of United Airlines Flight 93 in Pennsylvania , Grose testified before the US Congress on behalf of the NTSB , presenting findings of the Board 's formal investigation into the attacks
United Airlines Flight 93
United Airlines Flight 93
Vernon L. Grose