The fan blade which caused the failure of a Pratt & Whitney jet engine on a United Airlines passenger jet from Denver to Hawaii had been used for just 3,000 flights since its last inspection.

The plane’s engine caught fire, causing debris to fall over surburban areas of Denver on Saturday. The National Transportion Safety Board (NTSB) revealed that metal fatigue had caused the fan blade to break off shortly after take off. The plane was able to land safely with just minor damage to the fuselage. No one was hurt.

FAA ordered inspections between 6,500 to 7,000 flights

The US Federal Aviation Administration had required additional inspections of blades on PW4000 models with 112-inch fans following a 2018 failure on another United flight to Hawaii. The FAA order called for initial inspections starting after blades had completed between 6,500 and 7,000 flight cycles.

The fan blade’s inspection history was quoted in an earlier report by Reuters. An investigation into the 2018 failure found that inspections had missed a growing crack. Following the investigation, the NTSB reported that the company had inspected more than 9,000 blades.

The FAA issued an emergency order on Tuesday requiring all fan blades on Pratt & Whitney models used on the 777 to be tested before planes could return to carrying passengers.

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