It all began when a panel fell off mid-flight from one of its aircraft flown by Alaska Airlines. That set off a cascade of unfortunate events, including the fallout over the death of two whistleblowers within two months who had accused the Seattle-based company of taking shortcuts to manufacture its flagship jets. It’s also crucially led to delays in the delivery of its planes. 

With the summer just around the corner, airlines could do with these problems being solved ahead of peak travel time. However, as Boeing trails behind on its deliveries, it’s only adding to carriers’ worries. 

Lufthansa’s CEO Carsten Spohr voiced his concern about Boeing’s delays, calling them “extremely annoying” as it’s costing the German aviation giant hefty sums of money, in an interview with Swiss news outlet Neue Zuercher Zeitung.

He’s the latest aviation industry chief to publicly lament how Boeing’s safety crisis is impacting their business. In February, Ryanair’s CEO Michael O’Leary said he wanted Boeing to pay his airline compensation as it “constrained” the budget carrier’s growth. 

Emirates CEO Sheikh Ahmed bin Saeed Al Maktoum said he wasn’t happy with the impact of delays in Boeing planes and hoped the aircraft maker’s management would make good on its promise to fix its issues soon, Bloomberg reported last week.  

While some airlines have proven relatively better equipped to deal with delivery delays, others have had to cut flights out of their schedule to cope with the lack of aircraft.

A key reason so many airlines have struggled is that Boeing is one of only two great airplane manufacturers, along with European rival Airbus. A slowdown in the Seattle-based company’s production may have meant more business for its competitor, but only to a certain extent as Airbus maxes out its production capacity. 

“Everyone has an interest in Boeing being able to build great aircraft more reliably again soon,” Lufthansa’s Spohr said, adding that he was “sure Boeing will get the problems under control.”

Fixing the problem

Perhaps the biggest challenge facing Boeing—and by extension its airline customers—at the moment is the production cap imposed by the Federal Aviation Administration (FAA) on Boeing’s cash cow 737 Max aircraft. 

It’s designed to ensure the highest quality for a plane that has had its fair share of high-profile problems, but has already hurt the company’s margins after just months. Amid all the chaos, Boeing has announced changes to its leadership, including CEO Dave Calhoun’s plan to step down at the end of this year and commercial airplane head Stan Deal’s retirement. 

For its part, Boeing said it’s “implementing a comprehensive action plan” to address an FAA audit into the 737 line’s production, which found several instances of alleged failure to meet manufacturing and quality control standards.  

Ryanair’s O’Leary said he welcomed the changes across Boeing’s management (which he once described as “headless chickens”), hoping that’d help the American company change course.

The world’s biggest airline companies are betting on Boeing pulling its act together so it doesn’t cause more than a blip in delivery delays. But Boeing has a long road to fixing its dented image and building trust as an aviation kingpin.  

Lufthansa didn’t immediately return Fortune’s request for comment.