"The FAA should have had much better visibility into what was happening at Boeing before Jan. 5," said FAA Administrator Mike Whitaker at a Senate Commerce Committee hearing.

He said the agency had permanently boosted the use of in-person inspectors and would visit a Boeing factory in South Carolina on Friday.

The FAA's approach before then "was too hands off, too focused on paperwork audits and not focused enough on inspections," Whitaker added. "We will utilize the full extent of our enforcement authority to ensure Boeing is held accountable for any noncompliance. We currently have multiple active investigations into Boeing."

Whitaker also said the agency will continue increased on-site presence at Boeing and its supplier Spirit AeroSystems "for the foreseeable future."

Whitaker said the FAA has "additional inspections at critical points of the production process."

Whitaker and said after the incident "the FAA changed its oversight approach and those changes are permanent. We have now supplemented our audits with more active, in-person oversight — the 'audit plus inspection' approach."

On May 30, Boeing delivered a comprehensive quality improvement plan delivered to the FAA after Whitaker in late February gave Boeing 90 days to develop a comprehensive plan to address "systemic quality-control issues."