Story highlights Engine fixes ordered for 176 Boeing 787 Dreamliners at 29 airlines worldwide

"Urgent safety issue" icing could force in-flight engine shut downs

Boeing says it's working with GE and has completed more than 40 engine reworks

(CNN) Describing it as an "urgent safety issue," the Federal Aviation Administration has ordered modifications on specific General Electric engines on some 787 Dreamliners because an icing problem could force those engines to shut down in flight.

Friday's FAA airworthiness directive stems from a January 29 incident aboard a 787 flying at about 20,000 feet.

"Ice shed from the fan blades ... causing the blades to rub against the fan case, resulting in engine vibration," GE Aviation spokesman Rick Kennedy told CNN. That forced an engine shut down and the aircraft landed safely with its remaining engine.

According to the FAA document, "Susceptibility to heavy fan blade rubs, if not corrected, could result in engine damage and a possible in-flight non-restartable power loss of one or both engines."

"The potential for common cause failure of both engines in flight is an urgent safety issue," the FAA document said.

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