The U.S. Federal Aviation Administration said it will increase its oversight of Boeing Co.’s production and manufacturing operations, a day after it opened a formal investigation into the planemaker over last week’s accident on a 737 Max 9 jet.

The regulator is conducting an audit of Boeing’s 737 Max 9 production line and suppliers, according to an emailed statement Friday. The FAA will also increase monitoring of so-called “in-service events” on the Max 9, and will consider bringing in a third party to oversee the planemaker’s inspections and quality-control system. 

The moves suggest a further erosion of confidence in Boeing’s ability to build aircraft safely on its own, in light of the panel blowout on Alaska Airlines Flight 1282. Federal regulators had already stepped up oversight of Boeing since a pair of 737 Max crashes in 2018 and 2019 killed 346 passengers and crew. FAA inspectors are required to sign off on every 737 and 787 prior to delivery, work it had previously delegated to employees of the planemaker.

“It is time to re-examine the delegation of authority and assess any associated safety risks,” FAA Administrator Mike Whitaker said in the statement. “The grounding of the 737-9 and the multiple production-related issues identified in recent years require us to look at every option to reduce risk.”

Boeing had no immediate comment on the FAA’s announcement early Friday.

Shares of Boeing fell 1.9 per cent as of 8:45 a.m. in New York, before the start of regular trading in New York. The stock had already declined 15 per cent this year through Thursday, after the incident on Jan. 5. Spirit AeroSystems Holdings Inc., which makes the door panel for Boeing, slid 1.9 per cent premarket.

The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737 Max 9 to service, the FAA said in the statement.

The regulator is taking a more aggressive stance after coming under fire for moving slowly to respond to other accidents, such as the eventual grounding of the 737 Max fleet following the two deadly crashes almost five years ago. 

This week, Wizz Air Holdings Plc Chief Executive Officer Jozsef Varadi called for stronger oversight from watchdogs, saying that it “almost feels like the manufacturers got married to the regulators.”

Boeing, which already is facing heavy scrutiny over a series of quality issues across its aircraft programs, is also under pressure from lawmakers following the incident. 

Senator Maria Cantwell of Washington, home to Boeing’s 737 operations, said the latest accident warrants additional scrutiny of both Boeing’s operations and its watchdog. In a letter to FAA Administrator Michael Whitaker on Thursday, Cantwell requested documents from agency safety audits of Boeing and Spirit AeroSystems over the last two years. 

In the accident last week, an almost-new 737 Max 9 saw a large panel of the left-side fuselage eject during flight, leaving passengers exposed to a gaping hole. Nobody was seriously injured and the plane returned safely, but pressure is building on Boeing and its senior management to explain the defect.

Regulators grounded 171 of the 737 Max 9 jets in operation after the Alaska accident to allow for inspections, prompting Max 9 operators to cancel hundreds of flights.

With assistance from Richard Clough and Ryan Beene.