United Airlines has removed all Boeing 777 aircraft that are powered by Pratt & Whitney 4000 series engines from its schedule.
The move, announced Sunday evening, came a day after an engine failure on one of those planes scattered debris over the Denver suburb of Broomfield, Colo., and forced the pilots to abruptly return the plane to nearby Denver Airport. No one died or was injured in the incident.
In a tweet, United called its decision to remove those 24 Boeing 777s voluntary. But it came on the same evening that FAA administrator Steve Dickson announced that he had directed his staff to issue a directive requiring an immediate step-up of inspections of 777 with Pratt & Whitney 4000-series engines.
"This will likely mean that some engines will be removed from service," Dickson said.
United is the only U.S. carrier with that engine type on its fleet, the FAA said. Outside the U.S., only South Korea and Japan are home to airlines using PW4000-series engines, the agency added. The Japan Civil Aviation Bureau has also grounded aircraft using those engines. Korean operators include Korean Air and Asiana.
The cowling from one of the engines of United Flight 328. The engine part barely missed hitting a house just outside of Denver on Saturday.
United Flight 328 was headed from Denver to Honolulu on Saturday with 229 passenger and 10 crew members aboard. Shortly after takeoff, one of the aircraft's two engines failed, showering a residential neighborhood, including a soccer field, with debris. Among the fallen items was the engine casing, called the cowling, which landed in a residential yard.
According to the National Transportation Safety Board (NTSB), two fan blades in the engine were fractured, while one was imbedded in the containment ring, which is designed to keep a broken fan blade inside the engine.
The remainder of the fan blades had damage to the tip and leading edges.
The NTSB has begun an investigation into the incident.
United currently has 52 Boeing 777s with PW4000-series engines in its fleet, the carrier said. Twenty-four of those were active prior to their removal from the schedule over the weekend, while the other 28 were already parked as a result of the pandemic. United also has 44 777s with alternative engines that will not be grounded.
Boeing said Sunday that globally, there were 69 in-service and 59 in-storage 777s powered by the PW4000-112 engine. The manufacturer recommended the suspension of all operations of the craft.