Boeing said CEO Dennis Muilenburg accompanied pilots aboard a successful 737 Max jet test flight on Wednesday.
“The flight crew performed different scenarios that exercised various aspects of the software changes to test failure conditions,” Boeing said in a statement. “The software update worked as designed, and the pilots landed safely at Boeing Field.”
The FAA and Boeing have been under a microscope since the crashes and the plane has been grounded since mid-March following the deadly accidents that killed all 346 people aboard the jets.
Boeing said it will continue testing the aircraft and submit its safety updates to the FAA once that’s complete “in the coming weeks.”
Flight data retrieved from both planes black boxes show striking similarities between the two crashes, investigators have said. Boeing’s MCAS system, which is designed to prevent the plane from stalling by pushing its nose down if it climbs too high too fast, is suspected as contributing to both crashes.
Boeing stock closed down almost 2 percent on Wednesday.