In late 2018, Ethiopian Airlines’ chief pilot sent an urgent message to Boeing, the manufacturer of the 737 Max airliner.

Barely a month earlier, a 737 Max operated by Lion Air of Indonesia had plunged into the sea, killing everyone on board. The cause appeared to be a problem with the plane’s flight control system.

The Ethiopian carrier also flew the 737 Max, and the chief pilot wanted more information from Boeing about the emergency procedures to follow if the same problem that doomed the Lion Air flight should recur. At the time, Boeing was providing detailed briefings to pilots in the United States who were asking the same types of questions.

But Boeing chose not to answer the Ethiopian pilot’s questions beyond referring him to a public document it had already issued after the Lion Air crash. Boeing said in its response that it was prohibited from giving additional information because it was providing technical support to Indonesian authorities investigating that crash.

Instead, Boeing briefly summarized the document, which is dated Nov. 6, 2018, and is called an operations manual bulletin, according to email exchanges between the chief pilot and Boeing made public after The New York Times initiated legal action to unseal filings in a related criminal case.

Three months after the request by Ethiopian Airlines, one of its 737 Max jets nosedived into the ground after takeoff from Addis Ababa, Ethiopia’s capital, killing all 157 people on board. The main cause was found to be the same flawed flight control system responsible for the Lion Air flight crash, a failure that presented the Ethiopian Airlines pilots with the very same kinds of life-or-death decisions about how to respond that the chief pilot had asked about months earlier.

While it is unclear whether the Ethiopian Airlines pilots could have avoided crashing had Boeing provided a more detailed response, aviation experts said the lack of additional information most likely contributed to the inability of the pilots to pull themselves out of a fatal nosedive once the flight control software system malfunctioned.

“Who knows what they would have done with the information, but not having it seals the deal,” said Dennis Tajer, a spokesperson for the Allied Pilots Association, which represents American Airlines pilots.“Any information given to the Ethiopian pilots, like we had, could have made the difference between life and death,” said Tajer, who is also a pilot who flies the 737 Max.

After the Lion Air crash, Boeing executives sought out U.S. pilots to brief them on topics that were not discussed with the Ethiopian pilots, including long-term strategies for improving flight safety.

Detailed U.S. briefing

The briefing for American pilots included a detailed explanation of the flight control system that failed, known as MCAS. Boeing executives touched on its operational role and spoke about technical issues vital to pilots, including how the system interacts with the angle-of-attack data, or the angle at which the wind strikes the wing. They aimed to enhance pilots’ comprehension of the system and to underscore the system’s complexity.

The company’s representatives highlighted efforts to address and clarify what they called misunderstandings related to MCAS. They pushed for training that would extend beyond routine checklists, focusing instead on equipping pilots with a thorough understanding of system behaviors and potential failures.

Despite the constraints Boeing described in the response to the Ethiopian chief pilot, Boeing officials discussed numerous details of the Lion Air crash.

Guidance sought

According to the email exchange with Ethiopian Airlines around the same time, the chief pilot happened to be seeking guidance similar to what was shared in the briefing. A few days after attending a teleconference Boeing held for all users of the 737 Max, or a fleet call, the pilot emailed to ask what to prioritize in the event of multiple emergencies involving MCAS and angle-of-attack data. Such emergencies could overwhelm pilots with caution lights, audible sounds and seemingly conflicting warnings.

Tajer, who attended the meeting Boeing held with American pilots and who put several questions to Boeing representatives himself, said: “Our meeting with Boeing covered the same questions that the Ethiopian pilots were asking. It’s clear that they had the same questions we had but did not get the answers that we got from Boeing.”

The emails obtained by the Times are being used by families of the victims of the crash as they pressure the Justice Department to take a harder line with Boeing over its culpability and to convince a federal judge to not accept a plea agreement reached between the company and federal prosecutors. And the emails support some of the conclusions of an investigation by the Ethiopian government.

The Ethiopian report, released in December 2022, found that if Boeing had provided more information to the carrier’s pilots about how to respond in the event of a software malfunction, they might have been able to regain control.