The catalyzing moment was last week, when CEOs of major U.S. MAX customers Southwest, United, Alaska, and American demanded to meet the board to express frustration at a lack of progress, sources said. Boeing Chairman Larry Kellner offered to set up bilateral meetings instead.

But over the weekend, Boeing’s board pre-empted that action - agreeing to staggered departures of Calhoun, Kellner and planemaking CEO Stan Deal, whose post went to chief operating officer Stephanie Pope. A senior industry source described the shakeup as Boeing management being “fired by its customers.”

Insiders noted it was the broadest top-level clear-out since CEO Phil Condit resigned days after the company’s finance director was fired in a defense-contract scandal in 2003. “The U.S. carriers were determined to force regime change,” said a source familiar with the discussions.