Leaders at the top of major airlines from Emirates to Southwest have aired their frustration with the jet maker as deliveries run behind schedule. Southwest, United and American have blamed slowdowns in hiring and changed flight plans on Boeing’s delays.

“Boeing needs to become a better company,” Southwest CEO Bob Jordan said at a JPMorgan industry conference in March, an uncharacteristically strong comment from the leader of the all-Boeing 737 airline.

Even if planes arrive late, compensation doesn’t often make up for the shortfall of jets.

“I’m not in the compensation business. I’m the airline business,” Etihad Airways CEO Antonoaldo Neves said in an interview.

Tight supply at both Boeing and Airbus makes shifting orders over to the European company nearly impossible. Both companies are sold out of narrow-body planes through almost the end of the decade. Boeing has an order book of more than 5,400 jetliners, after accounting adjustments, while Airbus has about 8,000 unfilled orders.

And Airbus isn’t on solid ground either, warning customers and investors last month that supply chain problems will slow its planned ramp up in production and slow deliveries.

Earlier this year as airline executives’ patience wore thin, they sought meetings with Boeing’s board chairman, people familiar with the matter said.

Shortly afterward, Boeing in March announced a leadership shake-up, with the head of its all-important commercial airplane unit replaced. CEO Calhoun, an alumnus of General Electric and Blackstone, said he would step down by the end of the year. Boeing replaced its chairman, too, installing ex-Qualcomm CEO Steve Mollenkopf.

Boeing hasn’t yet named a replacement for Calhoun. The CEO of Spirit AeroSystems, Pat Shanahan, who previously worked at Boeing and served as former deputy secretary and acting secretary of defense under former President Donald Trump, is considered a strong contender.

Across the airline industry, executives publicly and privately say they would rather Boeing take the time to fix problems than face prolonged uncertainty over when new planes will be delivered.

The 108-year old Boeing has a firm place in American history. Its bombers were crucial in World War II. It has built presidential aircraft. Former Presidents Barack Obama and Donald Trump have each held events Boeing 787 Dreamliner factories. And in space, a Boeing-built rocket propelled Apollo 11 to the moon in 1969.

Most of the general public knows Boeing as the company to usher in the jet age. It designed and launched four aircraft in just over a decade, including the first 737.

The narrow-body plane was soon dwarfed by Boeing’s groundbreaking and more glamorous jumbo jet, the 747, which could fit more than 500 people, and in some configurations, a piano bar. The 737 was dubbed “Baby Boeing” and went on to become the company’s bestseller, helping to make Boeing the largest U.S. exporter. It has built more than 11,000 of the 737s to date.

“Without Boeing, the world is a worse place,” AerCap’s Kelly said.

Last year, it looked like Boeing was back on a better footing.

“I have heard those outside our company wondering if we’ve lost a step. I view it as quite the opposite,” Calhoun said in note to employees last October.

Months later, the powerful blast from the Alaska Airlines door plug blowout ripped off head rests, seatbacks and the first officer’s headset, leaving a gaping hole in row 26. The incident terrified passengers and exposed the most serious in a series of quality control issues on Boeing jets. Previous issues included mis-drilled holes and incorrect spacing on some of Boeing fuselages.

The manufacturer’s production portfolio includes a host of jets that are regularly flown commercially around the world: the workhorse 737, the wide-body 787 Dreamliner, and soon, once approved by regulators, the 777X.

And while production flaws make headlines, Boeing jets continue to carry travelers safely around the world, with more than 13,000 at the end of last year. The company has a 45% market share of commercial jets currently flying, according to AeroDynamic Advisory.

Across all of its divisions, its customers also include the U.S. and foreign militaries, and NASA — and some of those units haven’t been without issue either.

“Our airplanes have carried the equivalent of more than double the population of the planet,” Calhoun said in testimony to a Senate panel last month for a hearing titled “Boeing’s Broken Safety Culture.”

“Getting this right is critical for our company, for the customers who fly our planes every day, and for our country,” he said. He apologized during the hearing to the family members of the Lion Air and Ethiopian crash victims, as they held posters with pictures of lost loved ones.

Critics say a yearslong push to reward Boeing shareholders and lower costs came at the expense of building totally new aircraft, in favor of updating older models. Boeing also outsourced production of key parts to suppliers that it increasingly put under pressure to deliver, exposing the supply chain to potential flaws.

United CEO Scott Kirby told CNBC in January that he believes the issues date back to Boeing’s merger with competing airplane manufacturer McDonnell Douglas in 1997. The tie-up is often cited as a turning point for Boeing that replaced its once engineering-led culture with a greater focus on returns.

From 2010 to 2019, Boeing spent $68 billion on stock buybacks and dividends, according to Melius Research analyst Rob Spingarn.

“This is a long time building,” Kirby said.

Calhoun, when asked about outsourcing production to Spirit, told CNBC in January: “Did it go too far? Yeah … probably did, but now it’s here and now I gotta deal with it.”

Flaws on its planes have cost Boeing billions of dollars due to periods of production drops, delivery pauses and compensation to customers.

Boeing does say that it’s on the right track.

For one, it’s been forced to slow production of its planes. While painful in the near term because it drives up costs and deprives the company of new planes to hand over to customers, executives say it’s the way to make sure manufacturing flaws don’t reappear.

Jefferies estimates Boeing produced about 24 Max jets a month in the second quarter and could move to roughly 35 a month in the last three months of the year. Boeing has said it aims to increase rates to about 50 Max planes a month in the next few years.

It’s also brought employees into the recovery effort. The company has held so-called “stand-downs” at its factories to pause work and discuss problems on the line.

And its plea deal with the DOJ, if approved by a judge in the coming weeks, could allow the company to settle a federal probe with a roughly $244 million fine and a probationary period of three years, during which time an independent monitor would oversee quality control, and other conditions.

“We are taking comprehensive action today to strengthen safety and quality,” Calhoun said in his testimony before the Senate panel last month. “And, we know, as America’s premier aerospace manufacturer, this is what you and the flying public have every right to expect from us.”

Goldman Sachs aerospace analyst Noah Poponak said Boeing can “still make a product that’s a total marvel. If they can get their act together, I think their reputation can improve quickly.”

Promoting and building up the Boeing workforce will be key in the coming years, according to Alex Krutz, managing director of Patriot Industrial Partners, an aerospace consulting firm.

The company has more competition for new workers than in previous generations in the Seattle area, he said, because of rapid expansion of tech companies there in the past few decades, as well as engineering competition from the private space industry.

“Companies thrive or don’t based on leadership,” he said.

The International Association of Machinists and Aerospace Workers, District 751, which represents some 30,000 Boeing technicians in Washington State and Oregon, is currently in contract negotiations with company, seeking more than 40% raises and a seat on Boeing’s board.

“We have more leverage than we’ve ever had in our history,” said Jon Holden, president of IAM District 751. “There’s massive demand for new airplanes.”

Some analysts say designing a new plane could help attract talent and set the company up for years to come, a project that was largely set to the backburner after the crashes.

The advice of Richard Aboulafia, an longtime aerospace analyst and a managing director at AeroDynamic Advisory is simple: “Begin a new program, and say, ‘We’re a company with a future.'”