On February 20, 2021, United Airlines Flight 328 (UA328/UAL328), a scheduled U.S. domestic passenger flight from Denver to Honolulu, suffered catastrophic engine failure four minutes after takeoff from Denver International Airport (DEN). Parts departing from the engine cowling of the Boeing 777-222 aircraft resulted in a debris field at least 1 mile (1.6 km) long over suburban residential areas of Broomfield, Colorado. Falling debris was recorded by eyewitnesses using smartphone cameras and a dash cam. Debris fell through the roof of a private home and significantly damaged a parked vehicle.The engine failure resulted in an in-flight engine fire, extensive damage to the engine nacelle, and minor damage to the fuselage. Passengers also recorded video of the engine nacelle damage and in-flight fire and posted these to social media. The failed engine was a Pratt & Whitney (P&W) model PW4077 turbofan.The crew secured the failed engine, and the aircraft returned to Denver using the remaining working engine, landing without further incident 24 minutes after takeoff at 13:28 local time. There were no reported injuries to persons onboard or on the ground. The U.S. National Transportation Safety Board immediately began investigating.
Similar 777-200 series aircraft were quickly grounded by several national aviation authorities, including the U.S. Federal Aviation Administration, which issued an Emergency Airworthiness Directive requiring U.S. operators of airplanes equipped with similar Pratt & Whitney PW4000-112 series engines to inspect these engines' fan blades before further flight. Japan Air Lines, which had a similar incident in December 2020, retired all of its P&W-equipped Boeing 777-200s a year earlier than planned in March 2021. As of December 2021, United Airlines, which also had a similar incident in 2018, had not returned its P&W-equipped Boeing 777-200s to service yet.