March 28 (UPI) -- Boeing has completed and detailed a software fix for its 737 Max-class aircraft it says will improve the models' safety, as investigators in two countries seek the causes of two recent crashes.
The company said many of the updates were made in the last two weeks, after an Ethiopian Airlines Boeing 737 Max 8 crashed March 10 and killed all 157 aboard. An October crash involving another Max 8 in Indonesia killed 189.
The fixes and Boeing's plan for re-training pilots must now be approved by the Federal Aviation Administration, which is facing questions from Congress over its approval process. Once approved, the fix could take days to install in the entire fleet -- and longer to give pilots the additional training. Some analysts told CNBC that could take as many as 12 weeks before the planes are airborne again.
"We're working with customers and regulators around the world to restore faith in our industry and also to reaffirm our commitment to safety and to earning the trust for the flying public," Boeing Vice President Mike Sinnett told reporters Wednesday.
Boeing said the fix updates the airliner's automated Maneuvering Characteristics Augmentation System, or MCAS, to allow the system to disengage if it receives conflicting data. A modified alert indicator for pilots is also among the fixes.
The company said it will give enhanced training for all 737 pilots so they're more aware of how the automated system handles flight and how to disable it. The changes have been in development for weeks, but Boeing fully detailed them Wednesday.
"The software was put through hundreds of hours of analysis, laboratory testing, verification in a simulator and two test flights, including an in-flight certification test with Federal Aviation Administration representatives on board as observers," Boeing said in a statement announcing the upgrades.
"These updates reduce the crew's workload in non-normal flight situations and prevent erroneous data from causing [automated] activation."
Boeing said the changes ensure pilots will always have the ability to override the automated flight system and manually control the airplane, when needed.
Sinnett said making the software updates to each plane will take about an hour and will begin immediately. The Max 8 has been grounded worldwide and the similar Max 9 is also restricted from flying in the United States. U.S. carriers Southwest, American and United fly the 737 Max variants. Boeing's 737 Max 10 has not yet entered service and it's unclear whether it will also receive the updates.
Earlier Wednesday, the FAA told a Senate committee about plans to increase its oversight of air safety this summer.
Transportation Department Inspector General Calvin Scovel told lawmakers the changes are being made based on a 2015 report that says the FAA needs to improve oversight of the certification process.