By Carlo Versano

Boeing announced on Monday that Dennis Muilenburg, the aerospace giant's CEO, was resigning effective immediately. David Calhoun, Boeing's chairman, will replace Muilenburg as chief executive on Jan. 13. Until then, Boeing CFO Greg Smith will be elevated to interim CEO, the company said.

Boeing's board reportedly decided over the weekend that it was time for Muilenburg to leave, nearly 14 months to the day since a Boeing 737 Max operated by Lion Air crashed off the coast of Indonesia, sending the company into the biggest crisis in its corporate history. Less than six months after that Lion Air flight crashed, another Max jet operated by Ethiopian Airlines crashed. The two accidents, believed to be a combination of pilot error and faulty software, killed a combined 346 people.

Muilenburg was faulted for Boeing's early response to those two crashes, the second of which led to an unprecedented global grounding of the entire 737 Max fleet earlier this year. Since then, he became the face of the chastened company, testifying to Congress and apologizing to family members while Boeing technicians worked around the clock on a software fix to the system, known as MCAS, that's believed to have caused two otherwise routine commercial flights to fall from the sky.

Just last week, Muilenburg made the decision to temporarily stop production of the 737 Max entirely, at least until the FAA gave the go-ahead for the software fix. Then, over the weekend, the company took another morale hit when its Starliner space capsule had to abort an unmanned mission to the ISS because its internal clock was set wrong.

Shares of Boeing rose nearly 3 percent on the announcement of Muilenburg's departure.