The Federal Aviation Administration's (FAA) audit of Boeing's 737 MAX production process after a panel blew off an Alaska Airlines jet in January failed 33 of 89 tests, The New York Times reported on Monday.

In the wide-ranging investigation, Boeing failed a check which dealt with the component that blew off the jet, known as a door plug, according to the presentation viewed by NYT.

Supplier Spirit AeroSystems, which makes the fuselage for the MAX, passed six of thirteen audits and failed the rest, the report added.

Additionally, an audit at Spirit focusing on the door plug component found five problems and it failed the one which dealt with the installation of the component, NYT said.

The audit raised concerns about the technicians who carried out the work and found that the company "failed to determine the knowledge necessary for the operation of its processes," according to the report.

Other audits that Spirit failed included one that involved a cargo door and another that dealt with the installation of cockpit windows, it said.

The FAA, Boeing and Spirit AeroSystems did not immediately reply to a Reuters' request for comment.

Earlier in the day, U.S. Transportation Secretary Pete Buttigieg said he expects the plane maker to cooperate in investigations by the Justice Department and National Transportation Safety Board into the 737 MAX 9 mid-air emergency on Jan. 5.

Meanwhile, the FAA's Michael Whitaker said the agency and Boeing hope to define the milestones the manufacturer must meet in order to increase the MAX production rate in the next 30 days.

Last week, the agency said it found "non-compliance issues in Boeing's manufacturing process control, parts handling and storage, and product control."