The Federal Aviation Administration has found multiple problems with Boeing’s production practices, follow a six-week audit of Boeing triggered by the January 5 door plug blowout on an Alaska Airlines Boeing 737 Max 9.

“The FAA identified non-compliance issues in Boeing’s manufacturing process control, parts handling and storage, and product control,” the FAA said in a press release, but did not immediately provide further details.

A separate report launched prior to the door plug incident but released last month found “gaps” in Boeing’s safety culture, including a disconnect between management and employees, and fears among employees about retaliation for reporting safety concerns.

The FAA said the findings of both this audit and the separate report should be part of Boeing’s quality improvement plan. It has given Boeing 90 days to produce the plan to fix its quality issues.

The audit also included major Boeing supplier Spirit AeroSystems, which builds the fuselages for the Boeing 737 Max 9 jet, among other items. Without giving details, the FAA said it found multiple instances where both companies allegedly failed to comply with manufacturing quality control requirements.

Boeing used to own the operations that now make up most of Spirit, but spun it off as a separate company in 2005. Boeing disclosed on Friday that it is in negotiations to possibly re-acquire Spirit.