The Federal Aviation Administration said Monday that a six-week audit of Boeing and one of its key suppliers, Spirit AeroSystems, revealed “multiple instances” in which the companies failed to meet quality control requirements.

As part of the audit, which looked at production of the Boeing 737 Max, the FAA said it “identified noncompliance issues in the control of Boeing’s manufacturing process, parts handling and storage, and product control.” The regulator has not publicly released further details.

The FAA initiated the audit after a door panel on a 737 Max 9 jet came loose at about 16,000 feet in early January, raising new questions about quality control practices at Boeing and Spirit, which could damage the fuselage or body of the 737 Max.

Boeing did not immediately comment. A Spirit spokesman, Joe Buccino, said the company was reviewing the findings and “in communication with Boeing and the FAA regarding appropriate corrective actions.”

The incident involving the door panel, known as a door plug, occurred on an Alaska Airlines flight shortly after it took off from Portland, Oregon, on January 5. The FAA quickly grounded similar Max 9 jets, even though the planes were allowed to do so. to be put back into use later that month after inspection.

In a preliminary report last month, the National Transportation Safety Board said four bolts used to secure the door plug had been removed from the plane at Boeing’s plant in Renton, Washington. The report suggested that the bolts may not have been reinstalled before the aircraft entered service.

The FAA audit was one of several steps the regulator took in the wake of the through-plug episode to step up oversight of Boeing’s manufacturing processes. The agency also opened an investigation into whether the aircraft manufacturer had failed to ensure its products were safe and conformed to approved design, and it banned the company from increasing production of the 737 Max series until quality control issues were resolved.

Last week, the FAA gave Boeing 90 days to develop a plan to improve quality control practices. The planemaker has already announced a leadership change in its commercial aircraft division, saying Friday it was in talks to acquire Spirit, which it founded nearly two decades ago.

JetBlue Airways and Spirit Airlines announced Monday they would abandon their planned $3.8 billion merger after federal antitrust regulators successfully challenged the deal in court. JetBlue said it would pay Spirit $69 million to terminate the deal.

A federal judge in Boston blocked the proposed merger on Jan. 16, siding with the Justice Department in ruling that the merger would reduce competition in the industry and give airlines more leeway to raise ticket prices. The judge, William G. Young of the US District Court for the District of Massachusetts, noted that Spirit played a crucial role in the market as a low-cost airline and that travelers would have fewer options if JetBlue were to take over.

“We are proud of the work we have done together with Spirit to set a vision to challenge the status quo, but given the hurdles to closure that remain, we have decided together that the interests of both airlines would be better served by moving forward independently,” said JetBlue’s chief executive, Joanna Geraghty, said in a statement on Monday. “We wish all the best for the entire Spirit team.”

JetBlue and Spirit appealed Judge Young’s decision. JetBlue filed an appeal letter last week arguing that the deal should go forward.

But in a filing with regulators on Jan. 26, JetBlue said it could terminate the deal. Spirit said in its own filing the same day that it believed there was “no basis to terminate the agreement.”

The merger agreement, which expired on January 28, could have been extended until July 24 if certain conditions were met. But JetBlue suggested in its January filing that Spirit had failed to meet some of its obligations under the agreement, giving JetBlue the option to walk away.

As part of the merger agreement, JetBlue agreed to pay Spirit and its shareholders $470 million in fees if the deal was blocked. Some legal experts said JetBlue may have been positioning itself to dispute the rest of those fees by terminating the agreement.

Spirit is heavily indebted and last made a profit before the Covid-19 pandemic. Investors see a merger as a lifeline for the company. The stock price has lost more than half its value since the ruling blocking the merger.

JetBlue shares rose on the same news, as investors see the end of the deal as a cost-cutting measure.

A merger of the airlines would have given the combined company greater market share, which is dominated by four airlines: American Airlines, Delta Air Lines, Southwest Airlines and United Airlines.

Alaska Airlines has also announced plans to increase its size. In December, it said it wanted to acquire Hawaiian Airlines for $1.9 billion. That deal is also likely to draw the attention of federal antitrust regulators.

Boeing said Friday it was in talks to acquire Spirit AeroSystems, a struggling supplier the manufacturer founded nearly two decades ago that makes the 737 Max bodies.

By reabsorbing Spirit, Boeing would attempt to rescue and restructure a troubled but important partner, which has been plagued by years of losses and quality control problems. Spirit’s problems have also at times limited how quickly Boeing can produce Max planes, the most popular commercial aircraft.

Bringing Spirit, one of the company’s key suppliers, back in-house would be a major strategic change for Boeing, which has long relied on outsourcing to make its planes. That strategy has come under increasing scrutiny amid concerns about Boeing’s quality problems.

Both companies have faced intense scrutiny since Jan. 5, when a panel on a 737 Max 9 exploded shortly after takeoff on an Alaska Airlines flight, exposing passengers to deafening winds at 16,000 feet. The pilots flying the plane landed it safely with no serious injuries reported. Experts say the event could have been catastrophic if it had occurred at higher altitudes as passengers moved around the cabin.

The National Transportation Safety Board said in a report last month that the plane appeared to have left a Boeing factory without the bolts needed to hold the panel, known as a door plug, in place. Door plugs are used to close gaps in the body of an aircraft where an emergency exit would have been installed if the aircraft had the maximum number of seats.

The incident followed two crashes of Max 8 jets in 2018 and 2019, which together killed almost 350 people. Aviation regulators grounded Max planes for nearly two years after those crashes. That crisis cost Boeing about $20 billion.

The acquisition of Spirit could allow Boeing to more easily change the supplier’s policies and manufacturing practices, something the company has been seeking from the outside for a few years. Quality and operations issues led to a leadership change at Spirit last fall. Patrick Shanahan, a former Boeing employee and senior Defense Department official, took over as CEO of Spirit.

“We believe that the reintegration of Boeing and Spirit AeroSystems manufacturing operations would further strengthen aviation safety, improve quality and serve the interests of our customers, employees and shareholders,” Boeing said in a statement.

“While there can be no guarantee that we will be able to reach an agreement,” the company added, “we are committed to finding ways to ensure the safety and quality of the aircraft that millions of people depend on every day.” keep improving. .”

But buying Spirit could also saddle Boeing with more problems at more factories as regulators demand the company improve quality control at its own plants. The Federal Aviation Administration this week gave the company 90 days to come up with a plan to address the quality control problems.

Spirit and other companies that make aircraft body and wing components have faced significant challenges in recent years, said Kevin Michaels, director of consulting firm AeroDynamic Advisory.

“It’s kind of a failed market,” he says. “The largest aviation companies are losing large amounts of money.”

Boeing sold Spirit to an investment firm in 2005 as part of a campaign to cut costs and focus more on aircraft final assembly. That investment company, Onex, based in Toronto, later listed Spirit on the stock exchange. Spirit soon began earning consistent annual profits of hundreds of millions of dollars.

But the company suffered a setback in the early 2010s, after the financial crisis. Its fortunes improved in the middle of the decade, but Spirit and its peers have suffered recently in part as aircraft makers like Boeing and Airbus have pressured suppliers to cut costs even as jets have become more complicated, he said. Mr. Michaels.

Spirit also suffered a major blow when regulators grounded the Boeing 737 Max jets after the two crashes. Then, in early 2020, the pandemic disrupted supply chains, contributing to rising material costs. Over the past four years, Spirit has lost $2.5 billion.

Any deal between Boeing and Spirit will impact Airbus, Boeing’s main competitor in commercial aircraft, because Spirit makes parts for Airbus aircraft, at. Airbus, based in Toulouse, France, declined to comment Friday on whether it would acquire Spirit’s units that supply it with parts.

Spirit’s shares closed down about 15 percent on Friday after The Wall Street Journal and other news organizations reported that Boeing was in talks to acquire the supplier. Boeing shares fell about 2 percent.

Liz Alderman reporting contributed.

JetBlue Airways said Friday it could pull out of its $3.8 billion acquisition of Spirit Airlines after a federal judge blocked the deal.

The announcement comes just a week after JetBlue and Spirit said they would appeal the decision, which was made in an antitrust case brought by the Justice Department.

In a regulatory filing On Friday, JetBlue said the deal could be terminated after Sunday if certain conditions are not met. Spirit said in his own file that it disagreed with JetBlue's assertion and believed there is “no basis to terminate the deal.”

A federal judge in Boston blocked the proposed merger on Jan. 16, ruling that Spirit plays a key role in keeping airfares low and that a takeover by JetBlue would hurt travelers. The ruling was a victory for the Justice Department, which under President Biden has sought to limit corporate consolidation across the economy.

The companies said last week they were preparing an appeal. As part of the merger agreement, JetBlue agreed to pay Spirit and its shareholders a combined $470 million if regulators blocked the deal.

Spirit's stock price fell about 16 percent Friday morning. The shares have lost more than half their value since the deal was blocked as the company is unprofitable and investors worry the airline is taking on too much debt. Spirit has also been forced to ground some of its jets due to an engine problem.

The stock price of JetBlue, which could save billions of dollars by not appealing and moving forward with the deal, was up slightly Friday morning.

Spirit Airlines, once a fast-growing low-cost carrier, is struggling to convince investors it has a clear path forward after an antitrust ruling blocked the company's sale to JetBlue Airways.

A federal judge in Boston blocked the proposed merger on Tuesday, agreeing with the Justice Department that the deal would harm consumers by limiting their choices and raising rates. The airlines, which could appeal, say they are considering their options.

Before inking a deal with JetBlue in July 2022, Spirit was struggling. Unlike larger airlines, it never fully recovered from the early days of the pandemic in 2020. The budget carrier is losing money, and some analysts say it's hard to see how Spirit can pull itself out of its financial hole, other than finding another airline. buyer. Some aviation experts say the airline may have to file for bankruptcy protection.

“It's a challenging financial picture for the company,” said Xavier Smith, director of energy and industrial research at AlphaSense.

In the three days since the ruling, Spirit's shares have lost more than half their value, from about $15 to $5.70. Shares fell sharply on Thursday after The Wall Street Journal reported that Spirit was exploring restructuring options.

Asked about that report, the company said it was “not pursuing nor involved in any legal restructuring.”

Spirit, like other airlines, has paid down a lot of debt during the pandemic but has not seen the financial recovery that larger airlines have seen. The company now has about $6.6 billion in debt, down from $3.6 billion in 2019. This month, the company sold and leased back 25 aircraft, helping it reduce its debt by $465 million.

“Spirit has taken and will continue to take prudent steps to ensure the strength of its balance sheet and ongoing operations,” the company said in a statement Thursday.

Unlike larger airlines such as Delta Air Lines and United Airlines, Spirit flies primarily within the United States; the few international routes are relatively short. As a result, the country has been unable to achieve the strong profits that many larger airlines have made on flights to Europe or Asia, and is more exposed to fierce price wars on US routes.

Additionally, Spirit's expenses have increased more than 60 percent since 2019 due to higher wages for pilots and flight attendants and more expensive jet fuel.

The airline is also experiencing problems with Pratt & Whitney engines in some of its aircraft. Spirit has grounded 26 of its nearly 200 jets after the supplier revealed manufacturing defects.

Analysts say there are two likely outcomes for Spirit: Another airline could acquire the company, or the company could use a bankruptcy filing to restructure its debt or sell its assets.

At its current valuation, Spirit could be an attractive option for an airline looking to expand. Buying another airline is often the easiest and most efficient way to grow, as there are few or no gates available at popular airports. There is also a shortage of aircraft because the two main manufacturers – Airbus and Boeing – have order books that can stretch to five years.

Frontier Airlines, which proposed buying Spirit before JetBlue outbid it, or another low-cost carrier would likely have the easiest time gaining antitrust approval, said Dylan Carson, an attorney with Manatt, Phelps & Phillips.

“That, I think, has the potential to secure the blessing of antitrust enforcers,” said Mr. Carson, a former Justice Department antitrust lawyer.

Frontier's cash-and-stock deal with Spirit was worth about $2.8 billion, compared to the $3.8 billion that JetBlue was willing to pay. Now that Spirit's valuation has fallen, another airline may be able to strike a deal at a lower price.

But Frontier's stock price has also fallen more than 60 percent since the offer to buy Spirit, which could pose a challenge for a new bid. Frontier planned to use stock to pay for part of the earlier deal. A Frontier representative declined to comment on whether it would consider another offer for Spirit.

Of course, Sprit's fortunes could improve if demand for domestic air travel grows significantly, although most analysts don't expect that to happen anytime soon.

Spirit is known for its no-nonsense experience. It has more seats on its planes than other airlines, giving passengers less legroom. The company charges for carry-on luggage, which is included with other airlines. Because many of its customers fly to save money, Spirit has limited ability to increase fares.

Kerry Tan, a professor at Loyola University Maryland who has studied airline fares, said that when Spirit offered service on a particular route, its competitors were forced to lower their prices.

“In my view, the worst-case scenario is that Spirit disappears and we are left with a less competitive environment,” said Dr. Tan.

Judge William G. Young said in his ruling this week that if the proposed merger goes through, JetBlue would absorb an airline that charged very low prices, significantly shrinking the category of such airlines and raising fares.

“Spirit is a small airline,” he said in the ruling. “But there are people who love it. To Spirit's dedicated customers, this one's for you.”

Madison Lee, a budget travel blogger, is one of those people.

She said Spirit's cheap flights and influence on other airlines' prices gave Americans “an equal opportunity to travel.” Ms Lee, 25, has visited 60 countries, mostly on budget airlines.

“It may not come with all the bells and whistles, you may not feel as comfortable, but honestly, for a lot of people, the purpose of traveling is not necessarily to be comfortable,” she said. “The mind gets the job done.”

A federal judge on Tuesday blocked JetBlue Airways' proposed $3.8 billion acquisition of Spirit Airlines, a victory for the Justice Department, which argued the deal would hurt travelers.

In his ruling, Judge William G. Young of the US District Court for the District of Massachusetts sided with the Justice Department in determining that the merger would reduce competition in the airline industry.

The proposed merger would have created the country's fifth largest airline. The Justice Department had argued that smaller, low-cost airlines like Spirit help keep fares low and that it would have hurt consumers if the company were acquired by JetBlue, which tends to charge higher prices.

This is a development story. Check back for updates.