The company has been named as a defendant in growing number of suits filed by families of passengers killed in a Lion Air crash off the coast of Indonesia on October 29 and an Ethiopian Airlines crash on March 10.
Muilenburg said he recently joined one of 96 test flights during which Boeing crew performed different scenarios that exercised the software changes in multiple flight conditions over 159 hours of air time.
The company said that the new inductions will bring down flight cancellations to nil while helping in the company's global and domestic expansion plans.
"The software update functioned as designed", he said, without indicating when Boeing will deliver the fix to global regulators for their review, which is expected to last around 90 days.
In both cases, faulty information from a sensor caused anti-stall automation to kick in when it wasn't needed and push the plane's nose down.
Muilenburg did not say when Boeing 737 Max planes may begin flying again. Pilots were unable to save the planes. Muilenburg also said Boeing representatives have held meetings in the U.S., the U.K., Singapore and China with pilots and officials from most of the airlines that own Max jets.More news: Professional Sports Gambler Breaks Most Money Won In A Single ‘Jeopardy’ Game
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Airlines have stopped ordering Boeing 737 Max planes, according to company's first quarter sales data, a troubling sign for the future of what was previously its fastest selling airplane.
It removed all 34 of its Max 8 jets from service on March 13 following two deadly crashes involving other airlines.
The report also showed a dip in deliveries of all 737 models, including the older 737-800, which fell to 89 this year, a major decrease from 132 last year during the same period.
Muilenburg said the software update would make the 737 MAX safe by preventing erroneous sensor readings from triggering an anti-crash system known as the Maneuvering Characteristics Augmentation System (MCAS).
A Boeing spokesman said the company's planes are equipped with "all critical features" necessary for safety. And it has said it will now provide two features that were missing in the two crashed planes free of charge.