China News Service, March 7 reported that the US National Transportation Safety Board (NTSB) said on the 5th that preliminary investigations confirmed that the Boeing 777 passenger aircraft engine fire and debris falling accident occurred in February, one of the reasons is metal fatigue.

Data map: On February 21, local time, debris falling from the engine of a United Airlines plane was found in a residential area near Broomfield on the outskirts of Denver, Colorado.

  A United Airlines Boeing 777 airliner flew to Hawaii in February shortly after takeoff, the Pratt & Whitney engine on the plane caught fire and some parts began to fall, and then returned to Denver.

No one was injured in this incident, but it raised questions about the maintenance and repair of the Boeing 777 aircraft.

  NTSB updated data confirmed that the engine fan blades of this passenger plane had fallen off and stated that "the fractured surface conforms to the (metal) fatigue characteristics".

This confirms the NTSB's initial discovery of metal fatigue, which refers to the weakening of the effectiveness of materials due to pressure after repeated use.

  However, the NTSB also pointed out that it has not yet made a final conclusion on the cause of the accident.

  The agency is still investigating and sending the damaged fan blades to Pratt & Whitney's metallurgical laboratory for further inspection by a senior metallurgist from NTSB.

  After the accident, Boeing 777 aircraft using the same engine were grounded worldwide, and the Federal Aviation Administration ordered inspections of all Pratt & Whitney engines.