The Roots of Boeing’s 737 Max Crisis: A Regulator Relaxes Its Oversight

One of the managers, Julie Alger, delegated the review of MCAS. Previously, the F.A.A. had the final say over the system.

The F.A.A. said that decision reflected the consensus of the team.

Boeing was in the middle of overhauling MCAS. To help pilots control the plane and avoid a stall, the company allowed MCAS to trigger at low speeds, rather than just at high speeds. The overhauled version would move the stabilizer by as much as 2.5 degrees each time it triggered, significantly pushing down the nose of the plane. The earlier version moved the stabilizer by 0.6 degrees.

When company engineers analyzed the change, they figured that the system had not become any riskier, according to two people familiar with Boeing’s discussions on the matter. They assumed that pilots would respond to a malfunction in three seconds, quickly bringing the nose of the plane back up. In their view, any problems would be less dangerous at low speeds.

So the company never submitted an updated safety assessment of those changes to the agency. In several briefings in 2016, an F.A.A. test pilot learned the details of the system from Boeing. But the two F.A.A. engineers didn’t understand that MCAS could move the tail as much as 2.5 degrees, according to two people familiar with their thinking.

Under the impression the system was insignificant, officials didn’t require Boeing to tell pilots about MCAS. When the company asked to remove mention of MCAS from the pilot’s manual, the agency agreed. The F.A.A. also did not mention the software in 30 pages of detailed descriptions noting differences between the Max and the previous iteration of the 737.

Days after the Lion Air crash, the agency invited Boeing executives to the F.A.A.’s Seattle headquarters, according to two people with knowledge of the matter. The officials sat incredulous as Boeing executives explained details about the system that they didn’t know.

In the middle of the conversation, an F.A.A. employee, one of the people said, interrupted to ask a question on the minds of several agency engineers: Why hadn’t Boeing updated the safety analysis of a system that had become so dangerous?