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.

Boeing's shares fell 5% on June 12 after an Air India 787-8 Dreamliner jet crashed minutes after taking off, posing a major setback for the planemaker as its new CEO looks to rebuild trust following a series of safety and production challenges.