Boeing found cracks in the structure of its 777X jetliner in initial test flights, the latest setback for the long-delayed airplane.
The company said it would ground its four-plane test fleet while it replaces the faulty component and sorts out what went wrong.
Boeing has orders for 540 of the new aircraft that it plans to start delivering in 2025. It is unclear what impact the issue could have on the plane’s launch date.
The 777X, designed for airlines wanting to connect the globe’s major cities and to carry some 400 passengers more, is already years behind. Boeing unveiled the plane in 2013 and said it would start delivering the model in 2020.
The company started flight-certification testing in July.
“During scheduled maintenance, we identified a component that did not perform as designed,” the company said. “Our team is replacing the part and capturing any learnings from the component and will resume flight testing when ready.”
The company described the part as a structural component between the engine and the airplane. It said no test flights were planned in the near term on any of the aircraft, and that it has notified federal regulators and customers.
The development was earlier reported by trade publication the Air Current.
Boeing’s efforts to launch new aircraft iterations face fresh delays amid a quality crisis that has engulfed the jet maker following January’s near catastrophe on an Alaska Airlines flight. The company also is awaiting federal certification of its MAX 10 and MAX 7 jets, also behind schedule.
Write to Sharon Terlep at sharon.terlep@wsj.com