Boeing says it has completed its updates to the flight-control software on the 737 MAX and tested it for more than 360 hours on 207 flights, after two deadly crashes resulted in the grounding of the aircraft globally, including in India.
The 737 Max 8 and 9 models were grounded worldwide after an Ethiopian Airlines crash on March 10 that investigators have described as appearing similar to a Lion Air crash on October 29 last year. A total of 346 people died in the two crashes.
In both accidents, the automated Maneuvering Characteristics Augmentation System (MCAS), pushed the planes' noses down while the pilots struggled to regain control.
"With safety as our clear priority, we have completed all of the engineering test flights for the software update and are preparing for the final certification flight," Boeing Chairman, President and Chief Executive Officer Dennis Muilenburg said on Thursday.
The update is expected to prevent erroneous angle of attack sensor readings from triggering the MCAS, something that initial investigation reports indicate occurred in both accidents involving Max aircraft.
He said in a statement that Boeing has completed development of the updated software for the 737 MAX, along with associated simulator testing and the company's engineering test flight.
To date, Boeing has flown the 737 MAX with updated MCAS software for more than 360 hours on 207 flights, he said.
The statement comes ahead of an international gathering of aviation regulators in Dallas next week to discuss the reviews of the Max.
Boeing is now providing additional information to address Federal Aviation Administration (FAA) requests 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.
"We are committed to providing the FAA and global regulators all the information they need, and to getting it right. We are making clear and steady progress and are confident that the 737 MAX with updated MCAS software will be one of the safest airplanes ever to fly.
He said the two accidents have only intensified Boeing's commitment to its values, including safety, quality and integrity, because "we know lives depend on what we do".
In addition, Boeing has developed enhanced training and education materials that are now being reviewed with the FAA, global regulators, and airline customers to support return-to-service and longer-term operations.
This includes a series of regional customer conferences being conducted around the world, the statement said.
The company has said its fix will feed MCAS with data from two, rather than just one, sensor, making the plane less susceptible to a crash because of bad data, CNN reported.
It will also make the system less potent, which is expected to prevent the steep dives seen in the two crashes, and provide additional training materials, it said.
All Boeing 737 Max aircraft being operated by Indian carriers have been grounded since the Ethiopian Airlines crash in March.
SpiceJet has been most affected by the grounding of 737 Max aircraft as it has 12 of them in its fleet. Jet Airways has not been affected as its five 737 Max aircraft have already been grounded - even before the grounding decision of the government -- due to non-payment of dues to lessors.
Meanwhile, multiple investigations, including the initial crash investigation, are ongoing. Criminal prosecutors, congressional staffers, and the Transportation Department inspector general are reviewing the initial certification of the 737 and the FAA's processes.
The FAA's aircraft certification chief, Earl Lawrence, told Congress on Wednesday the agency has been reviewing a preliminary version of the software provided by Boeing.
"I would call it the beta version," Lawrence said. "The reason why they submitted it to us is so we can stick it in the simulator so we could test it, so we can also look at their system safety analysis and see whether it will appropriately address it."
Pilots are expected to undergo extra training on the new system once it receives certification.
Aviation safety analyst Todd Curtis told the BBC that it would take a lot to convince the pilots and other flight crew members that the Boeing MAX aircraft was safe.