"Metal fatigue" is now the preferred avenue for the authorities to explain the spectacular incident that occurred last week on a United Airlines flight in the United States.
A Boeing 777-220 which had just taken off Saturday from Denver (Colorado) for Honolulu (Hawaii) had seen its right engine catch on fire and lose its fairing, and the pilots had to make an emergency U-turn.
As the plane returned to the airport, a shower of debris fell on a residential area in suburban Denver.
The American aircraft manufacturer had recommended Sunday evening the suspension of flights of the 128 aircraft concerned in the world, and a spokeswoman confirmed Monday that they were all immobilized.
The Federal Aviation Regulatory Authority (FAA) has ordered additional inspections on these Boeing 777s powered by Pratt & Whitney and the National Transportation Safety Board (NTSB) is also investigating the incident.
"A preliminary on-site examination indicates damage consistent with metal fatigue," Robert Sumwalt, chairman of the NTSB said Monday.
He also confirmed that two of the fan blades had been damaged.
One of them was found on a soccer field, the other remained lodged in the engine.
New test for Boeing
FAA officials met with representatives from Boeing and Pratt & Whitney on Sunday evening.
The US engine manufacturer said he was cooperating with the NTSB and “will continue to work to ensure the safe operation of the fleet”.
United Airlines, for its part, has decided to withdraw the aircraft from its flight schedule and "will continue to work closely with regulators to determine additional steps."
plane spreads debris over neighborhoods in Denver
The United Kingdom decided on Monday to ban its airspace to the Boeing 777s concerned.
And Japan's Transport Ministry said it had ordered more stringent inspections of the Pratt & Whitney engine after a Japan Airlines (JAL) 777 flying from Tokyo Haneda Airport to Naha on the island of Okinawa, experienced problems with "one engine from the same family" in December.
The incident is a new setback for the aircraft manufacturer, whose share lost more than 2% Monday on the stock market.
Boeing is barely recovering from the 737 MAX crisis, its flagship aircraft which was grounded in May 2019 after two accidents that killed 346 people.
After nearly two years of ban, a modification of the flight control software and the implementation of new pilot training protocols, this model was recently authorized to fly again.
Boeing is also, like its rival Airbus, affected by the Covid-19 pandemic and its catastrophic consequences on international air transport.
This health crisis led to the cancellation of orders for hundreds of devices.
The Dutch authorities also announced Monday the opening of two investigations after the fall two days earlier of debris from a Boeing 747-400 cargo plane, which injured two people in the south of the Netherlands.
Several experts believe, however, that the 777 incident in the United States is more of a maintenance or engine problem than of the design of the plane by Boeing.
In service for more than twenty-five years without major accident, the device "has a very solid reputation", underlined Michel Merluzeau, expert of the AIR firm.
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The current problem "has nothing to compare" with the crisis of the Boeing 737 MAX, also estimated Richard Aboulafia, an analyst of the Teal Group, specialist in aeronautics.
“After all these years of service it's unlikely that this is an engine design issue, it's definitely something to do with maintenance,” he said.