CHICAGO/SEATTLE (Reuters) – Boeing Co plans to cut its monthly 737 production by nearly 20 percent as it works to manage the grounding of its MAX aircraft in the wake of two deadly crashes, Chief Executive Officer Dennis Muilenburg said on Friday.

Deliveries of Boeing’s best-selling aircraft were frozen after a global grounding of the narrowbody model following the crash of an Ethiopian Airlines jet on March 10, killing all 157 people onboard.

Starting mid-April, production will be cut to 42 airplanes per month from 52, the company said in a statement.

The crash of a Lion Air plane in Indonesia last October that killed all 189 people on board and the crash in Ethiopia have left the world’s largest planemaker in crisis as its top-selling jetliner is grounded worldwide.

Muilenburg said the company now knows that a chain of events caused both disasters, with erroneous activation of so-called MCAS anti-stall software “a common link” between the two.

Boeing said it would not reduce jobs at the new production rate and will work to minimize the financial impact.

Boeing’s board will establish a committee to review how the company designs and develops airplanes, Muilenburg added. The group will “recommend improvements to our policies and procedures” for its 737 MAX and other airplane programs.

Boeing said it continues to make progress on a 737 MAX software update to prevent further accidents.

Shares in Boeing Co fell around one percent after the market closed on Friday.

Boeing faces logistical issues in finding places to park the growing number of grounded 737 MAX planes as well as being responsible for all their maintenance costs since it has been unable to deliver the jets to customers, two people briefed on the situation said.

Manufacturers avoid halting and then resuming production as this disrupts supply chains and can cause industrial snags. Boeing had been planning to speed up production again in June to 57 a month.

Having to hold planes in storage without delivering them does, however, consume extra cash through increased inventory.

Separately, National Transportation Safety Board (NTSB) chairman Robert Sumwalt told reporters that U.S. investigators were given the raw data from Ethiopian Airlines Flight 302 as soon as it was read in France last month. He added that the Ethiopian Airlines 302 preliminary report “was very thorough and well done.”

Former NTSB chairman Christopher Hart, who was named by the Federal Aviation Administration this week to head an international team to review the safety of the Boeing 737 MAX, told reporters Friday he thought the review, which will start Monday, could take about three months. It is still not clear what countries will take part.

He said investigators are going to be focused far more on the interaction between software and pilots rather than mechanical issues in future. “This is territory we are going to see more of,” Hart said.