The Federal Aviation Administration and Boeing made key mistakes certifying the new complex software system on the 737 Max that is now blamed for crashes in Indonesia and Ethiopia and led to a worldwide grounding of the aircraft, according to a new report that adds more scrutiny to the process of approving passenger airplanes.

The report from the Joint Authorities Technical Review panel and commissioned by the FAA criticizes both the government agency and Boeing for the certification process that allowed the faulty MCAS software.

The 737 Max process shows the FAA needs to spend more time accounting for human factors with pilots when certifying new elements on planes, hire more inspectors to oversee new aircraft and update policies to deal with increasingly complex systems, the report said. It also urged the FAA to share safety information with foreign aviation authorities.

“The (committee) found that the MCAS was not evaluated as a complete and integrated function in the certification documents that were submitted to the FAA,” the report said.

The report was submitted Friday to the FAA by a group made up of aviation authorities, including former National Transportation Safety Board Chairman Christopher Hart and representatives from the FAA, National Aeronautics and Space Administration and aviation officials from China, Canada and the European Union, among others.

The panel was discouraged from reviewing how and if the 737 Max should be recertified to fly again.

“Today’s unprecedented U.S. safety record was built on the willingness of aviation professionals to embrace hard lessons and to seek continuous improvement,” said a statement from FAA Administrator Stephen Dickson, who took over the job in July.

In a statement, a spokesman for Boeing said the company welcomes the review and is working with the FAA to improve the process to certify planes.

The FAA review backs up recommendations on the certification process made by the NTSB in September, including a need to reevaluate pilot response.

The report on the 737 Max comes as airlines, including Texas-based American and Southwest, wait for approval to fly the 737 Max again. American and Southwest don’t expect to fly the plane again until at least January. The grounding has put significant strains on operations at American and Southwest, which operated the largest fleets in the U.S. of 737 Max planes.

The FAA ordered the review in June after taking criticism for allowing the plane to fly back in 2017.

At the heart of the report is Boeing’s MCAS system, a software designed to help keep the plane flying level at high speeds after larger, more fuel-efficient engines were added to the updated 737 model. But that software didn’t always react as anticipated. Reports from crashes that killed 346 people in Indonesia and Ethiopia showed that pilots struggled to handle planes equipped with MCAS, which stands for the Maneuvering Characteristics Augmentation System.

The FAA report released Friday said the agency needs to update its policies for determining how long it takes pilots to recognize and respond to problems.

Another problem, the report said, was certifying an updated plane based on an old model. Because the 737 Max was based on the original 737 from 1967, the FAA didn’t perform the needed analysis on design changes, including MCAS, the report said. One recommendation said that in the future, the regulatory agency should put more scrutiny into new systems on old plane designs.

The report also said Boeing failed to share critical information on the disputed software system and the FAA needs more inspectors to handle these kinds of projects.

Investigations from The Seattle Times, The New York Times and The Wall Street Journal said FAA inspectors delegated authority and expertise to Boeing’s engineering teams, who were under pressure to rush the plane to delivery.

The FAA’s report backed that up and said there were signs of “undue pressure,” which “further erodes the level of assurance in the system of delegation.”

However, the review backed up the long-standing practice of delegating some elements of inspections to teams at airline manufacturers, something criticized in the aftermath of the 737 Max crashes. But only if done properly.

“With adequate FAA engagement and oversight, the extent of delegation does not in itself compromise safety,” the report said. “However, in the 737 Max program, the FAA had inadequate awareness of the MCAS function.”