(Bloomberg) -- The Federal Aviation Administration’s top official said the agency may expand its probe of Boeing Co.’s manufacturing practices beyond the 737 Max assembly operations if it finds evidence of problems elsewhere at the planemaker.

For now, the agency is focused on the mid-cabin door plugs on Max 9 aircraft like the one that blew off an Alaska Airlines flight shortly after takeoff on Jan. 5, according to FAA Administrator Mike Whitaker. Airlines have reported finding loose bolts in their fleets of Max 9s after they were grounded by the agency following the accident.

“Boeing manufactures a number of aircraft, so we’re going to look at the Max, but we’ll also look at the company systemically to see whether these issues run elsewhere,” Whitaker said in an interview. “It depends on where the evidence leads us.”

A Boeing representative declined to comment.

A broader inquiry would heap additional pressure on a company dealing with a growing crisis of confidence. The intensified scrutiny follows a string of quality lapses that have bedeviled Boeing’s Max operations since two fatal crashes in 2018 and 2019 killed 346 people.

The agency’s latest examination has so far found issues with workmanship that point to manufacturing deficiencies rather than design flaws, Whitaker said. 

“Given that there is a history there, which we can’t ignore, our focus is really on the quality control and the manufacturing process,” he said.

Airlines meanwhile continue to operate without the Max 9 in their fleets. Whitaker declined to discuss how quickly the agency would allow flights to resume.

Boeing isn’t delivering newly built Max 9 planes equipped with the plug doors while the grounding is in effect, Whitaker said. Deliveries of those planes cannot resume until the FAA approves the inspection procedures that must be performed to end the grounding for the existing fleet, according to the agency. 

“There is no time frame,” he said. “It will happen when we know that this aircraft is safe to fly.”

Separately, Boeing plans to pause the assembly lines at its 737 factory near Seattle for one day on Jan. 25 to hold meetings focused on quality with plant employees. Boeing said it would host similar sessions at all of its commercial aircraft plants and fabrication sites over the next few weeks.

(Updates to add 737 assembly line pause in final paragraph.)

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