Shortly after takeoff at 1:30 in the afternoon on Saturday, February 20, United Airlines Flight 328 was climbing to cruising altitude out of Denver International Airport when an explosion rocked the plane. The cowling of the right wing engine blew off, and several passengers recorded video of the naked engine spewing flames and wobbling as the plane returned to the ground, and—thankfully—landed safely.

The explosion took place over suburban Denver, where people on the ground also recorded the cloud of smoke and falling debris. Pieces of the engine and the adjacent wing were scattered over a mile-wide stretch of the city. Most notable was the 12′-wide circular cowling, which landed in the bed of one homeowner’s pickup truck. The pickup truck is so far the only known casualty of the incident.

UA Flight 328 was a Boeing 777 powered by Pratt & Whitney PW4000-112 engines. United Airlines has 52 of these planes, and is the only US airline to fly them. Another 76 are in operation worldwide. An identical UA plane had a very similar engine failure en route to Hawaii in February 2018.

The international response was swift. By Sunday morning, Japan had directed that no such plane would be allowed to enter their airspace without fresh inspections. The EU followed suit a few hours later. And on Tuesday, the FAA ordered that all planes operating Pratt & Whitney PW4000 engines be grounded pending a thorough investigation, an action which United Airlines had already taken.

“After reviewing the available data and considering other safety factors, the FAA determined that operators must conduct a thermal acoustic image inspection of the large titanium fan blades located at the front of each engine,” FAA officials said in a statement. The current theory is that a cracked fan blade caused the explosion, and a TAI will detect any other cracks that may be forming.

Image credit: Markus Mainka /