More than 2,000 family members of those killed when a Boeing 737 Max crashed in Ethiopia filed formal opposition Thursday to technical fixes the Federal Aviation Administration has proposed for the plane, saying they still do not believe the aircraft will be safe.

“We believe that the FAA is more concerned with saving Boeing’s investment in the 737 MAX than it is on ensuring that the airplane is safe,” the family members wrote in response to a proposed FAA directive for operators of the plane.

The fixes focus on changes to a software system implicated in two crashes of the 737 Max that happened over a span of five months in 2018 and 2019. The system was designed to smooth the planes’ handling, but malfunctioned before the crashes, driving down the jets’ noses in a way the pilots were unable to overcome. A total of 346 people died in the two crashes and the Max fleet was grounded worldwide while Boeing developed a fix.

The relatives of people who died in the second crash, which happened shortly after the plane took off from Addis Ababa on March 10, 2019, wrote that updating the faulty software was insufficient.

“The FAA should reevaluate the airplane as a whole and only permit it to fly if the FAA is completely satisfied that the 737 MAX is not a danger,” they wrote.

The FAA, in a statement, said it would “carefully consider all comments as we finalize the Airworthiness Directive.”

The families submitted their comments the day after the House Transportation Committee issued a scathing report on the development of the Max by Boeing, its oversight by the FAA and their response in the months between the two crashes.

House investigators concluded that the crashes were the result of a “horrific culmination of a series of faulty technical assumptions by Boeing’s engineers, a lack of transparency on the part of Boeing’s management, and grossly insufficient oversight by the FAA.”

In their comments, the family members wrote that investigative findings showing missed opportunities to make the planes safer mean “the pain of our loss is compounded.”

Boeing engineers and test pilots flagged concerns inside the company about how the software system worked, concluding in one case that if pilots didn’t respond to a malfunction within 10 seconds, the outcome would be catastrophic.

“Boeing engineers identified the exact defect that would later cause the two crashes but decided that it was not necessary to change the design to eliminate the system’s risks,” the family members wrote.

The families called for a more thorough review of Max, including by an independent panel of experts, and the release of more data to the public before the plane is cleared to fly again.

The FAA is proposing to require software changes developed by Boeing that would curb the system and that rely on data from two sensors instead of one.

The family members argue the changes only paper over an underlying issue with the plane’s aerodynamics. The software was included to counter changes in the jet’s handling compared with previous models of 737, caused by the placement of the Max’s new engines.

“The software updates and revised procedures are no more than a mitigation strategy, because they fail to address the root cause of the problem,” they wrote.

An organization representing more than 10,000 British pilots filed comments Wednesday, echoing some of the families’ concerns. The group said in particular that it would prefer for the software system to receive data from three sensors, an approach used by European manufacturer Airbus.

The public has until Monday to comment on the FAA’s proposal. The agency will then review the comments before issuing a final directive requiring operators of the jets to make the fixes, a key step toward ungrounding the fleet.

But it remains unclear exactly when the Max might be approved to fly again.

An international group of regulators and crews has been meeting at London’s Gatwick Airport this week to evaluate training changes for Max pilots, and their feedback will be incorporated into a second document that the FAA will give the public the opportunity to comment on.

The FAA has repeatedly said it is not following a specific timeline but is focused on thoroughly reviewing the Max.