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 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