NTSB Chair Jennifer Homendy stated that Ethiopia's Aircraft Investigation Bureau (EAIB) had mistakes in its report.
"We feel what they did not do is really delve into the flight crew performance issues and whether they were adequately prepared," Homendy said.
"We felt like it was not as comprehensive and robust as it could have been."
The fatal crashes of the Boeing 737 MAX in Indonesia and Ethiopia in 2018 and 2019 resulted in a 20-month grounding of the plane, causing a cost of more than $20 billion for Boeing. The plane was eventually cleared to fly again after the company made changes to software and pilot training.
The National Transportation Safety Board (NTSB) was not given the opportunity to review or provide feedback on Ethiopia's final report before it was released to the public last month, an infraction of regulations established by the International Civil Aviation Organization (ICAO), according to NTSB Chair Jennifer Homendy.
"It's unprecedented; under ICAO, we get a right to review the report and to provide comment," Homendy said.
The NTSB had previously stated that Ethiopian investigators who were examining the cause of the March 2019 Ethiopian Airlines crash had not sufficiently focused on crew training and emergency procedures in their report.
