After holding out for days as other countries halted flights aboard Boeing’s 737 MAX, U.S. authorities on Wednesday grounded the Renton-built model that has crashed twice in the last five months, saying “new evidence” pointed toward similarities between two crashes that together killed nearly 350 people.

The Federal Aviation Administration (FAA) said Wednesday it had received “newly refined satellite data” from Sunday’s Ethiopian Airlines crash, along with “new information from the wreckage concerning the aircraft’s configuration just after takeoff,” that indicates parallels to October’s Lion Air crash.

Those “warrant further investigation of the possibility of a shared cause for the two incidents that needs to be better understood and addressed,” acting FAA administrator Daniel Elwell said in an emergency order grounding the flights.

Both crashes involved recently delivered Boeing 737 MAX 8 models that crashed within minutes of takeoff.

With the latest data, “it became clear to all parties that the track of the Ethiopian flight was very close and behaved very similarly to the Lion Air flight,” Elwell told reporters.

Data from the October crash in Indonesia, which killed all 189 people aboard, showed the pilots were fighting against a new flight control system on the MAX — the Maneuvering Characteristics Augmentation System, or MCAS — that repeatedly pushed the airplane’s nose down due to a faulty sensor.

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It’s too soon to know the cause of Sunday’s Ethiopian crash, which killed all 157 people on board. Officials said Wednesday they would send the black box to France for analysis.

Ethiopian Airlines CEO Tewolde Gebremariam told CNN on Tuesday that the pilot of the flight that crashed reported “flight control problems” and asked to return to the airport, a request captured in recorded conversations with air traffic controllers. He added that the similarities between the Lion Air and Ethiopian crashes were “substantial,” noting both planes were new and crashed shortly after takeoff.

The FAA’s decision to ground the MAX 8 and MAX 9 models, announced by President Donald Trump, came after nearly every other country, from Europe to China, had already halted flights over potential safety concerns. Canada, the only other significant holdout, grounded the jets earlier Wednesday, before the United States did.

“Boeing is an incredible company. They are working very, very hard right now,” Trump told reporters at the White House. “Hopefully they’ll very quickly come up with the answer. But until they do, the planes are grounded.”

New satellite data

In Canada, Transport Minister Marc Garneau also said that new satellite data showed similarities between the two crashes. He said the information allowed his agency’s experts to track data points such as the fluctuations in the vertical profile of the aircraft.

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“This is not conclusive, but it is something that points possibly in that direction,” he said of the similarities. “And, at this point, we feel that threshold has been crossed and that’s why we are taking these measures.”

Aircraft-tracking company Aireon said it provided Canada the real-time satellite tracking data, which shows the plane’s activity for the duration of the flight.

The company had also provided the data on Monday to U.S. authorities, including the National Transportation Safety Board and the FAA, said company spokeswoman Jessie Hillenbrand.

Elwell said investigators were skeptical of the initial flight path information but reviewed refined data from Aireon Wednesday that was clearer. He declined to comment on the physical evidence found at the crash site.

While Trump announced the news, Elwell told reporters he, as acting FAA boss, ultimately made the decision to temporarily ground the MAX aircraft. He declined to say how long the emergency order might last.

Impact on Boeing

The decision is a blow to Boeing, where the 50-year-old 737 product line, and the MAX version that now dominates production, is a cash cow. The first completed MAX plane was delivered in 2017, and there are now nearly 400 in operation around the world. At the end of January, Boeing had a massive backlog of 4,661 MAXs on order.

CEO Dennis Muilenburg called Trump on Tuesday to reiterate that the company believed the MAX aircraft was safe, and the two reportedly talked again Wednesday.

“We are supporting this proactive step out of an abundance of caution,” Muilenburg said in a statement following Trump’s announcement. “We are doing everything we can to understand the cause of the accidents, in partnership with the investigators, deploy safety enhancements and help ensure this does not happen again.”

Boeing stock ended up slightly for the day after diving following the initial grounding order. It is down about 11 percent since Friday’s close.

The company has been working on a software fix for the plane’s MCAS system but its completion is not required before the FAA may lift the emergency ground order, Elwell said.

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In the United States, Southwest, American and United airlines all fly the 737 MAX — they have about 65 MAX aircraft among them. SeaTac-based Alaska Airlines does not have any in operation but has the larger MAX 9 on order.

Pilot concerns

According to a NASA database where pilots can anonymously flag safety issues, shortly after the Lion Air crash two pilots reported they had experienced unexpected “nose down” problems with the 737 MAX during takeoffs of their flights. Both wrote that they corrected the problem by disconnecting the autopilot, with one of the pilots noting “concerns with the MAX 8 nose down stuff.” Those incidents weren’t connected to the MCAS system, however, which does not operate when the plane is in autopilot mode.

A third pilot complained about the same time that some systems such as MCAS are not fully described in the flight manual. In a lengthy critique, the pilot wrote:

“I think it is unconscionable that a manufacturer, the FAA, and the airlines would have pilots flying an airplane without adequately training, or even providing available resources and sufficient documentation to understand the highly complex systems that differentiate this aircraft from prior models. The fact that this airplane requires such jury rigging to fly is a red flag. Now we know the systems employed are error prone — even if the pilots aren’t sure what those systems are, what redundancies are in place, and failure modes.

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“I am left to wonder: what else don’t I know? The Flight Manual is inadequate and almost criminally insufficient. All airlines that operate the MAX must insist that Boeing incorporate ALL systems in their manuals.”

House Democrats vowed Wednesday to conduct “rigorous oversight” to get to the bottom of the FAA’s decision-making process.

“Despite repeated assurances from the FAA in recent days, it has become abundantly clear to us that not only should the 737 MAX be grounded but also that there must be a rigorous investigation into why the aircraft, which has critical safety systems that did not exist on prior models, was certified without requiring additional pilot training,” said a statement from U.S. Rep Rick Larsen, D-WA, chair of the House Subcommittee on Aviation, and Peter DeFazio, D-OR, chair of the House Transportation and Infrastructure Committee.

At Seattle-Tacoma International Airport, only about three MAX flights operate each day, all from Southwest Airlines, and airport operations were not affected, said spokesman Perry Cooper.

Seattle Times staff reporter Steve Miletich contributed to this story.

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