WASHINGTON/CHICAGO (Reuters) – Boeing Co is making “steady progress” on the path to certifying a software update to the grounded 737 MAX and has made the final test flight before a certification flight, its chief executive said on Wednesday.

FILE PHOTO: Boeing Chairman, President and CEO Dennis Muilenburg speaks during a delivery celebration of the Boeing KC-46 Pegasus aerial refueling tanker to the U.S. Air Force in Everett, Washington, U.S., January 24, 2019. REUTERS/Lindsey Wasson/File Photo

Boeing’s newest 737 model, the MAX, was grounded worldwide in March following two fatal crashes, one on Lion Air in Indonesia on Oct. 29 and another on Ethiopian Airlines on March 10, which together killed all 346 on board.

Battling its biggest crisis in years, the world’s largest aircraft manufacturer