F.A.A. Investigates Claims by Boeing Whistle-Blower About Flaws in 787 Dreamliner

The Federal Aviation Administration is investigating claims made by a Boeing engineer who says that sections of the fuselage of the 787 Dreamliner are improperly fastened together and could break apart mid-flight after thousands of trips.

The engineer, Sam Salehpour, who worked on the plane, detailed his allegations in interviews with The New York Times and in documents sent to the F.A.A. A spokesman for the agency confirmed that it was investigating the allegations but declined to comment on them.

Mr. Salehpour, whose résumé says he has worked at Boeing for more than a decade, said the problems with fastening the sections came about as a result of changes in how the enormous sections were fitted and fastened together in the manufacturing assembly line. The fuselages for the plane come in several pieces, all from different manufacturers, and they are not exactly the same shape where they fit together, he said.

Boeing concedes those manufacturing changes were made, but a spokesman for the company, Paul Lewis, said there was “no impact on durability or safe longevity of the airframe.”

Mr. Lewis said Boeing had done extensive testing on the Dreamliner and “determined that this is not an immediate safety of flight issue.”

“Our engineers are completing complex analysis to determine if there may be a long-term fatigue concern for the fleet in any area of the airplane,” Mr. Lewis said. “This would not become an issue for the in-service fleet for many years to come, if ever, and we are not rushing the team so that we can ensure that analysis is comprehensive.”