Boeing 737 Max airplanes sit parked at Boeing Field on November 18, 2020 in Seattle.
CNN  — 

The Federal Aviation Administration initially overrode its own engineers’ recommendations in 2019 to ground the Boeing 737 Max after a second fatal crash, according to a new watchdog report.

The inspector general for the Department of Transportation said investigators interviewed agency officials and reviewed evidence showing engineers at the FAA’s aircraft certification office overseeing Boeing “recommended grounding the airplane while the accident was being investigated based on what they perceived as similarities between” the two fatal crashes.

There was also competing data, the report said, suggesting the crashes were not related to the same system.

“Yet Agency officials at Headquarters and the Seattle ACO opted not to do so; instead, they waited for more detailed data to arrive,” the report concluded.

The conversations were taking place after the crash of Ethiopian Airlines Flight 302 on March 10, 2019. Lion Air Flight 610 crashed October 29, 2018. The crashes killed a combined 346 people.

The US did not ground the plane until three days after the crash, after every other country worldwide had. The grounding ultimately lasted nearly two years.

The inspector general report, released Friday, recommended the agency update and improve its policies for evaluating crashes and other events. The FAA told the inspector general it would make updates and develop formal training.

While awaiting additional data in March 2019, FAA officials issued an official notice backing up their decision to allow the Max to continue flying. An engineer drafted an analysis which showed the risk of fatalities to be 13 times higher than the relevant FAA standard. “However,” the inspector general’s report said, “this document was not completed and did not go through managerial review due to lack of detailed flight data.”

The inspector general concluded the FAA’s decision-making on the grounding after the second crash “aligned with its typical processes” by waiting for detailed data, but called the processes “outdated” and said officials are not uniformly trained on how to use them.

The FAA told the inspector general it is updating its guidelines for grounding an aircraft when it discovers an urgent safety issue, and told CNN in a statement it “concurs with the Inspector General’s recommendations.”

“The agency also identified the issues outlined in the report before it was issued and is working to address them,” the FAA said. “As we incorporate these recommendations, we also continue to look for additional opportunities to apply lessons learned from the Boeing 737 MAX’s return to service.”