File photo taken on June 19, 2017 shows a Boeing 737 Max 9 at the 52nd International Paris Air and Space Show in Bourget, France. (Xinhua/Chen Yichen)

SAN FRANCISCO, May 16 (Xinhua) -- Boeing said Thursday that it has completed software update and tests for 737 Max planes that have been grounded worldwide since March this year following two deadly air crashes in a short span of five months.

"Boeing has completed development of the updated software for the 737 MAX, along with associated simulator testing and the company's engineering test flight," said the U.S. top aircraft manufacturer.

It added that it has flown the 737 Max with an updated flight control system, the Maneuvering Characteristics Augmentation System (MCAS), for more than 360 hours on 207 flights.

Investigators believed a flaw in the MCAS software was a contributory factor to the crash of the Ethiopian Airlines Boeing 737 Max plane en route from Addis Ababa to Nairobi, Kenya, on March 10, 2019, which killed all 157 people aboard.

The crash bore alarming similarities to the circumstances surrounding an earlier fatal air accident involving another 737 Max aircraft of the Indonesian Lion Air, which went down in Indonesia in October last year and killed all 189 passengers and crew on board.

The two deadly air crashes have plunged Boeing in the worst crisis in its history, and the company has been under mounting pressure to improve air safety by updating the flight control system of the 737 Max planes.

Boeing said it is now providing additional information to address requests of the Federal Aviation Administration (FAA) that include detail on how pilots interact with the airplane controls and displays in different flight scenarios.

"Once the requests are addressed, Boeing will work with the FAA to schedule its certification test flight and submit final certification documentation," Boeing said.

Boeing President and CEO Dennis Muilenburg said the company has finished all of the engineering test flights for the software update and is preparing for the final certification flight.

Muilenburg expressed confidence that the updated MCAS software will make 737 Max aircraft "one of the safest airplanes ever to fly."

The FAA is planning a meeting next month in Texas with air regulators from around the world to review the update of the Boeing software fix and new training and education programs for pilots on airplanes with the updated flight control system.