Last year, the F.A.A. said it was also investigating claims by a Boeing engineer that parts of the fuselage, or body, of the Dreamliner were improperly fastened together, which the whistle-blower said could cause premature damage to the plane over years of use.

The deadly crash of Air India Flight 171 last week has centered renewed scrutiny on the airplane's manufacturer, Boeing. This time it's the 787 Dreamliner in investigators' sights. The accident, which killed over 270 people, was the first fatal crash for the Dreamliner since the model began flying in 2011.

The Boeing 787-8 models faced repeated scrutiny over safety and production practices. From John Barnett to Salehpour, Boeing whistleblowers had already warned of 787 Dreamliner concerns