Pressure is mounting on Boeing after Ethiopian investigators said pilots flying Ethiopian Airlines Flight 302 weren't responsible for the March 10 crash that killed 157 people, shifting blame to the flight-control system that's also suspected in an October crash of the same type of 737 Max jet.
The Ethiopian plane, which crashed just six minutes after take off from Addis Ababa, followed a similar flight pattern as the Lion Air flight that went down in Indonesia's Java Sea and killed all 189 passengers and crew five months earlier. Pilots of both planes appear to have had trouble regaining control of the aircraft after an automated flight control system, called MCAS, pushed the nose of the jets down to keep them from stalling.
"The crew performed all the procedures repeatedly provided by the manufacturer but was not able to control the aircraft," Ethiopian Transport Minister Dagmawit Moges told reporters at a news conference Thursday.
Investigators found that pilots on the Ethiopian flight turned the anti-stall system off and back on again to try to regain control of the plane, casting doubt on Boeing and the Federal Aviation Administration's assertions that the crash may have been avoided had pilots simply followed established safety procedures.
Moges didn't specifically blame the MCAS software. However, she said it needed to be reviewed before the planes, which have been grounded since mid-March, are allowed to fly again.
"Since repetitive uncommanded aircraft nose-down conditions are noticed ... it is recommend that the aircraft control system shall be reviewed by the manufacturer," Dagmawit said. She also suggested that the aviation authority ensures the jet's flight control system is reviewed by Boeing before the jets are allowed to fly again.
It's expected to take several months before they will issue a final report and announce the cause of the crash. The preliminary findings were based on flight data and cockpit voice records on the Boeing 737 Max.
Hours after Ethiopian investigators published their 30-page preliminary report, Boeing CEO Dennis Muilenburg released a statement and video acknowledging, for the first time, that bad data feeding into the MCAS system played a role in the crashes.
"With the release of the preliminary report of the Ethiopian Airlines flight 302 accident investigation it's apparent that in both flights the Maneuvering Characteristics Augmentation System, known as MCAS, activated in response to erroneous angle of attack information," Muilenberg said in a statement and video that was posted to the company's Twitter account Thursday.
"As pilots have told us, erroneous activation of the MCAS function can add to what is already a high workload environment," he said. "It's our responsibility to eliminate this risk. We own it and we know how to do it."
Boeing is currently under investigation by the U.S. Justice Department, the Transportation Department's inspector general and Congress.
The FAA formed an international task force with other aviation regulators to review Boeing's planned fixes for the plane. It said that its investigation is still in the early stages and that it would take "appropriate action" once more details become available.
The statement did not specify whether the FAA would review the Max's flight control system, as recommended by Ethiopian investigators.
Ethiopian Airlines said in a statement that the report clearly showed that the pilots were not at fault.
"Despite their hard work and full compliance with the emergency procedures, it was very unfortunate that they could not recover the airplane from the persistence of nose diving," the airline said.
Investigations into the two crashes are ongoing. Ethiopian officials said that a final report could take a year before release, and a final report on the Lion Air accident in Indonesia is expected in August.