Anti-stall system was activated before Ethiopian Airlines Boeing 737 MAX crash: Sources

Officials investigating the Ethiopian Airlines Boeing 737 MAX crash believe that a new automated stall-prevention system was activated before the plane dived into the ground, two sources briefed on the investigation told ABC News.

The automated system — known as Maneuvering Characteristics Augmentation System, or MCAS — is suspected to have played a role in both the Ethiopian Airlines crash and last year’s Lion Air crash, which killed 157 and 189 people, respectively.

These are the first details to emerge since Ethiopian investigators shared the fatal flight’s black box data with international aviation experts earlier this week.

Sources told ABC News that a preliminary report, which will include these findings on the Boeing 737 MAX MCAS system, is expected to be released soon.

Boeing met with top airline industry personnel and reporters just earlier this week to demonstrate proposed software updates that would make MCAS more difficult to automatically engage and easier for pilots to control. Boeing is still awaiting FAA approval on the software update.

American Airlines’ chief Boeing 737 pilot Roddy Guthrie told ABC News the proposed changes amount to “significant enhancements.”

“They were enhancements to a good system,” Guthrie said. “They put some checks and balances in the system. Now that will make the system much better.”

American Airlines, United Airlines and Southwest Airlines are the three U.S. carriers that fly the Boeing 737 MAX.

“The 737 family is a safe airplane family and the 737 MAX builds on that tremendous history of safety that we've seen for the last almost 50 years. We mourn this loss of life and we’re going to do everything we can do to ensure that accidents like these never happen again,” said Mike Sinnett, Boeing's vice president of product strategy, during the Wednesday demonstration.

Boeing 737 MAX jets have been grounded globally after the March 10 crash in Ethiopia. Data showed that the Ethiopian Airlines and Lion Air crashes were eerily similar, although final reports have not been released for either incident and a direct link could not be established as a result.

Boeing reminded the public this week that the MCAS system can be disengaged by pilots via two switches on the control panel followed by using the manual trim wheel next to them. It's unclear what prevented the Lion Air pilots from turning the system off, instead of fighting it. Investigators are still trying to determine what actions the Ethiopian Airlines pilots took in reaction to the MCAS activation before they crashed under — what appear to be so far — similar circumstances.

The Seattle-based manufacturer has since been scrutinized for its training practices leading up to the launch of the 737 MAX 8 jets, including public congressional hearings and an Inspector General investigation into the Department of Transportation’s certification process for the plane.

The FBI has also joined a criminal investigation to look into the certification of the Boeing 737 MAX 8.

“The safety of the American people, of all people, is our paramount concern,” President Donald Trump said in March.

ABC News Senior Transportation Correspondent David Kerley contributed to this report.