(NEW YORK) — Shares of Boeing have plunged nearly 10% this week after a door plug blew out of the company’s 737 Max 9 aircraft during an Alaska Airlines flight.

The incident, which took place on Friday night, prompted the Federal Aviation Administration to ground the aircraft.

The stock price of Spirit Aerosystems, the manufacturer of the door plug, has fallen by more than 11% since trading began on Monday.

The National Transportation Safety Board has opened an investigation into the incident. The Alaska Airlines flight, which carried 171 passengers, had taken off from the Portland International Airport and climbed to 16,000 feet when the door plug fell off the aircraft, according to the NTSB.

None of the passengers or crew members experienced serious injuries.

In a note to investors, Bank of America said the incident does not alter the firm’s previous recommendation that individuals buy shares of the stock. The bank, however, warned of a potential negative effect on public perception of Boeing.

“We do not expect this current issue to have a material impact to our 2024 financial forecast,” Bank of America said, adding, “We do see the latest incident as eroding the fragile confidence that has been built around the 737 Max franchise. In our view, Boeing needs to tread carefully and cautiously through this potential reputational minefield.”

On Monday, United Airlines said it had found loose bolts on its 737 Max 9 fleet during inspections ordered after Friday’s incident.

The NTSB investigation could expand to additional aircraft as the agency learns more, NTSB chief Jennifer Homendy told ABC News’ “Good Morning America” on Tuesday.

“At some point we may need to go broader,” Homendy said. “But right now we have to figure out how this occurred with this aircraft.”

In a statement on Saturday, Boeing backed the decision to ground its 737 Max 9 aircraft and investigate the incident.

“Safety is our top priority and we deeply regret the impact this event has had on our customers and their passengers,” the company said. “We agree with and fully support the FAA’s decision to require immediate inspections of 737-9 airplanes with the same configuration as the affected airplane.”

“We will remain in close contact with our regulator and customers,” the company added.

The renewed scrutiny arrives roughly five years after Boeing 737 Max aircraft were grounded worldwide following a pair of crashes in Indonesia and Ethiopia that killed a combined 346 people.

In 2021, after a two-year ban, Boeing 737 Max aircraft were permitted to fly.

In addition to the safety concerns, the company faced a pandemic-related decline in demand as well as a recent supply chain slowdown tied to flaws identified in the 737 Max.

Speaking on an earnings call in October, Boeing CEO Dave Calhoun acknowledged difficulties encountered by the company in recent months as it aims to reach full production.

“We have more work to do. But overall, we’re making progress in our recovery,” Calhoun said. “We knew 2023 would be a bumpy ride.”

Calhoun addressed scrutiny of the company’s culture as it tried to restore trust over the years following the deadly crashes.

“I’ve heard from a few of you wondering if we’ve lost a step in this recovery,” he said. “You might not be surprised to hear that I view it as exactly the opposite.”

“Over the last several years, we’ve added rigor around our quality processes,” he added. “We’ve worked hard to instill a culture of speaking up and transparently bringing forward any issue, no matter the size, so that we can get things right for a bright future.”

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