Following the widely-reported failure of an engine on a United Airlines flight departing from Denver airport Saturday, airlines are temporarily grounding dozens of Boeing 777s.

Boeing recommended suspending operation of the aircraft after an incident Saturday aboard United Flight 328, when one of the engines failed just minutes after the flight took off from Denver International Airport bound for Honolulu.

The damaged engine dropped debris across a wide area, as the jetliner returned to the airport and landed safely. No injuries reported either aboard the aircraft or on the ground.

The grounding affects some 69 in-service and 59 in-storage 777s powered by Pratt & Whitney 4000, according to a statement from Boeing. Only a handful of carriers operate this version of the 777, including United, Korean Air, Japan Airlines and ANA.

In a tweet United Airlines said, “We are voluntarily and temporarily removing 24 Boeing 777 aircraft powered by Pratt & Whitney 4000 series engines from our schedule. We will continue to work closely with regulators to determine any additional steps and expect only a small number of customers to be inconvenienced.”

Japan's transportation ministry ordered All Nippon Airways and Japan Airlines to ground the aircraft that use the Pratt & Whitney 4000 engines, and South Korea's Asiana Airlines, which owns nine of the planes, has pulled them from the schedule as well. Korean Air said Monday it is awaiting guidance from the country's transport ministry.

Meanwhile FAA administrator Steve Dickson said in a statement, “After consulting with my team of aviation safety experts about yesterday’s engine failure aboard a Boeing 777 airplane in Denver, I have directed them to order an Emergency Airworthiness Directive that would require immediate or stepped up inspections of Boeing 777 airplanes equipped with certain Pratt & Whitney P4000 engines. This will likely mean that some airplanes will be removed from service.”

Dickson’s statement pointed out that the Pratt & Whitney PW4077 engine uses “hollow fan blades that are unique to this model of engine, used solely on 777 airplanes.”

An initial examination of the failed engine by the National Transportation Safety Board showed that two fan blades were fractured, and the remaining blades were damaged. The NTSB said the findings are preliminary and that a final detailed report will be issued following its investigation.

Both Boeing and Pratt & Whitney – a subsidiary of Raytheon Technologies – said they are cooperating with the investigation into the Denver incident.

united.com, boeing.com