This has been a very difficult several months for Boeing chairman, president and CEO Dennis Muilenburg.

First, Lion Air Flight 610 -- a Boeing 737 MAX 8 aircraft -- crashed on October 29, 2018 shortly after takeoff from Soekarno-Hatta International Airport in Jakarta. All 189 passengers and crew died in the disaster.

Then, on March 10, 2019, Ethiopian Airlines Flight 302 -- another Boeing 737 MAX 8 aircraft -- crashed soon after takeoff from Addis Ababa Bole International Airport in Ethiopia. All 157 passengers and crew died in this latest disaster involving Boeing 737 MAX aircraft.

For the most part, CEO Muilenburg -- who the Seattle Times recently reported took home $30 million in compensation in 2018 -- has kept a low profile after this most recent crash.

That is, until yesterday.

On Sunday, Boeing's Dennis Muilenburg issued a statement on the accident investigation of Ethiopian Airlines Flight 302. The statement began with a note to the families and loved ones of the victims:

First and foremost, our deepest sympathies are with the families and loved ones of those onboard Ethiopian Airlines Flight 302.

The statement then went on to detail what Boeing is doing to address the problems with its 737 MAX aircraft:

Boeing continues to support the investigation, and is working with the authorities to evaluate new information as it becomes available. Safety is our highest priority as we design, build and support our airplanes. As part of our standard practice following any accident, we examine our aircraft design and operation, and when appropriate, institute product updates to further improve safety. While investigators continue to work to establish definitive conclusions, Boeing is finalizing its development of a previously-announced software update and pilot training revision that will address the MCAS flight control law's behavior in response to erroneous sensor inputs. We also continue to provide technical assistance at the request of and under the direction of the National Transportation Safety Board, the U.S. Accredited Representative working with Ethiopian investigators.

Earlier Sunday, Ethiopia's transport minister Dagmawit Moges said:

During the investigation of the FDR [flight data recorder], clear similarities were noted between Ethiopian Airlines Flight 302 and Indonesian Lion Air Flight 610, which will be the subject of further investigation.

While it's still too early to definitively determine what caused the two 737 MAX airplanes to crash, initial indications point to problems with angle-of-attack sensors mounted on the aircraft. According to a report in The Washington Post, "There are concerns it may have sent the wrong signals to new software on the flight that automatically dips the plane's nose to prevent a stall."

While it may be some time before Boeing 737 MAX airplanes are once again allowed to fly -- putting the grounded Southwest, American, and United planes back in the air -- it's clear that Dennis Muilenburg faces his biggest test as CEO of Boeing.

Will he rise to the challenge? Time will tell.