Rolls-Royce Holdings Plc fell the most in more than a year after the in-flight shutdown of one of its engines on an Airbus SE A350 jet raised concerns that the model may be the latest afflicted by a design defect.

The captain of the Iberia flight from New York to Madrid made an emergency landing in Boston 1 1/2 hours after takeoff when a technical failure was detected, the airline said Wednesday. The plane landed safely and engineers are currently evaluating the problem.

The incident with the Trent XWB engine that’s exclusive to the A350 stoked fears that glitches with the Trent 1000 model made for Boeing Co.’s 787 could carry over to the newer turbine. Rolls has previously said the XWB is based on a different architecture and “categorically” unaffected by the same flaws.

“We are aware of the issue and will be working closely with the airline to support them,” Rolls-Royce said by email following the Iberia incident, adding that it expects the engine to achieve market-leading levels of reliability.