Boeing has replaced the head of its commercial airplane unit, the company said Tuesday, amid a scramble to convince regulators to allow its 737 Max plane back in service after two fatal crashes that killed a total of 346 people.

Kevin McAllister is the most senior executive to leave in the wake of the catastrophe. The commercial airplane division has been immersed in a crisis for nearly a year following the first of two 737 Max crashes. A second 737 Max went down less than five months later, prompting a worldwide grounding of Boeing’s best-selling aircraft.

McAllister will be replaced by Stan Deal, a three-decade Boeing employee who most recently led its global services business, Boeing said.

The leadership change comes less than two weeks after Boeing’s board stripped CEO Dennis Muilenburg of his chairman role, saying the move would allow him to better focus on getting the Max planes back to service.

After the second crash, Boeing halted deliveries and slashed production of the planes. The grounding has rippled through Boeing’s supply chain and to airline customers who have been forced to cancel thousands of flights and forgo hundreds of millions of dollars in revenue.