The head of the Federal Aviation Administration has acknowledged his agency should have been more aware of problems at Boeing before a door plug blew off a 737 Max jet during an Alaska Airlines flight in January.

The top U.S. aviation regulator said Thursday that the Federal Aviation Administration should have been more aware of manufacturing problems inside Boeing before a panel blew off a 737 Max during an Alaska Airlines flight in January.

“FAA’s approach was too hands-off — too focused on paperwork audits and not focused enough on inspections,” FAA Administrator Mike Whitaker told a Senate committee.

Whitaker said that since the Jan. 5 blowout on the Alaska jetliner, the FAA has changed to “more active, comprehensive oversight” of Boeing. That includes, as he has said before, putting more inspectors in factories at Boeing and its chief supplier on the Max, Spirit AeroSystems.

Whitaker made the comments while his agency, the Justice Department and the National Transportation Safety Board continue investigations into the giant aircraft manufacturer. The FAA has limited Boeing’s production of 737 Max jets to 38 per month, but the company is building far fewer than that while it tries to fix quality-control problems.