The Federal Aviation Administrations audit of Boeing and Spirit AeroSystems found multiple instances in which the companies allegedly failed to comply with manufacturing quality control requirements, the agency said Monday.

The six-week investigation, which began after a Boeing 737 Max 9 lost a door panel during a flight in January, found issues with Boeings manufacturing process control, parts handling and storage, and product control, the FAA said in a news release, which didnt offer more detail.

FAA Administrator Mike Whitaker addressed the audits findings with Boeings CEO and other senior leaders in a meeting last week and gave the company 90 days to outline a plan of action, the FAA said. Boeing also must review and address a report released last week by a panel of outside experts that examined safety culture within the company dating back to two 737 Max 8 crashes in 2018 and 2019.