Regulators had criticised Muilenburg's efforts to reassure customers and the financial community that government approval of a fix for the MAX was coming soon -- optimism that repeatedly proved misplaced.

An engineer by training, Muilenburg appeared to often rely heavily on data and legal advice rather than diplomacy in formulating his response to the escalating crisis, and his approach sometimes exacerbated friction with customers and regulators.

His relationship with FAA leaders deteriorated to the point that about two weeks ago agency chief Steve Dickson publicly called out the company's failures to provide complete data supporting proposed MAX software fixes.

Boeing said David Calhoun, a longtime Boeing director with deep ties to the aviation and private-equity industries, will become CEO on January 13.

"The new leadership team made it clear in public statements Monday that they won't get ahead of regulators in predicting the return to service of the 737 MAX after its grounding in March following twin crashes that claimed 346 lives and one CEO.

After keeping assembly lines open and storing 400 planes to be ready for a return to flight, Boeing acknowledged this month it would not be able to reach its target of flying this year and announced it would halt 737 MAX production in January. 

Boeing said yesterday that shipments from 737 suppliers will be suspended for a month starting mid-January, adding that it was uncertain when production would restart.