Boeing has a delivery problem and it's not good for the airlines that rely on its planes

• American planemaker Boeing has paused some deliveries of its best-selling 737 MAX aircraft.
• The delays are due to a supplier's "non-standard manufacturing process" on the aft section of the fuselage.

Boeing has halted some deliveries of one of its most important aircraft — again.

On Thursday, Bloomberg reported the American planemaker would have to pause deliveries of its best-selling Boeing 737 MAX jet due to production issues.

Boeing confirmed the news to Insider, saying a supplier notified the company of a "non-standard manufacturing process" on the aft section of the fuselage of certain MAX planes. These include the MAX 7, MAX 8, and the MAX 8200, which is a high-capacity version of the MAX 8 variant. The MAX 9 will not be impacted.

The manufacturer said the problem is not a safety concern and current in-service planes can still fly, but warned the flaws will "affect a significant number of undelivered 737 MAX airplanes, both in production and in storage" while Boeing works to address the issue.

"We regret the impact that this issue will have on affected customers and are in contact with them concerning their delivery schedule," the company said.

The delay is bad news for airlines who are depending on deliveries of the airliner to grow capacity, launch new routes, and replace aging aircraft.

United Airlines, which has 80 MAX planes in its fleet and 433 on order, told Insider it does not expect the delays to have "any significant impact on our capacity plans for this summer or the rest of the year."

Meanwhile, American Airlines said it is aware of the pause and is "working with Boeing to understand how it may impact our MAX deliveries." American has 42 MAX planes in its fleet and 88 on order.

Southwest Airlines did not immediately respond to Insider's request for comment but told Reuters: "We are in discussions with Boeing to understand what that impact will be in 2023 and beyond."

The carrier has 137 MAX planes in its fleet with firm orders for 417, plus another 147 as options. In an annual filing on March 14, Southwest said it initially expected to receive approximately 100 MAX jets in 2023, but has since amended that to 90.

The delays are not expected to affect Delta Air Lines' order for MAX aircraft, which are exclusively for the largest option — the MAX 10. Deliveries are projected to start in 2025, though the variant is not yet certified — a process Boeing doesn't expect to complete until at least late 2023, the Seattle Times reported.

Though Boeing and its partners are still assessing the impact of the most recent delivery stoppage, delivery delays have become a serious trend for the planemaker.

Since 2019, deliveries of Boeing's 787 Dreamliner have been paused three different times due to production flaws that appear similar to the new MAX issues and concerns over the jet's inspection method.

American, in particular, voiced frustrations over the delayed 787s, and even had to adjust its summer 2023 schedule because of it. The carrier also had to cut some international flying last year for the same reason.

Richard Aboulafia, managing director of aviation consulting firm AeroDynamic Advisory, told Insider he does not anticipate Boeing's MAX delays to be as "invasive" as the planemaker's Dreamliner headache. Still, with history as our guide, nothing is certain.

Boeing's MAX program is in many ways still in recovery. The plane's grounding in 2019 saw a complete suspension of the program and a need to recertify the plane, a process that took years. Boeing then faced challenges clearing stockpiled aircraft and restarting production during the pandemic due to shortages.

While there is concern the MAX delivery delays could impact airline schedules, especially as the busy summer travel season fast approaches, Aboulafia explained the issue is likely to be more manageable than the Dreamliner.

"Boeing can keep building MAX 9s," he told Insider. "It's just going to be a question of supplier management, getting the alternate supplier that doesn't have these issues, and ramping up while correcting the issues with the affected supplier."

However, Bloomberg Intelligence aerospace industry analyst George Ferguson described the pause as "concerning" because the aircraft is "vital to Boeing's turnaround."

"Its importance likely means a remedy will be urgently pursued, though reworking it could be costly and an extended pause would significantly hurt commercial profit, cash generation, and the balance sheet," he said.

The 737 MAX and the 787 are important money-makers for Boeing. Since December alone, the manufacturer has garnered nearly 200 orders for the Dreamliner, including from United Airlines, Air India, and two Saudia Arabian carriers.

And, Boeing said despite its recent 787 delivery pause, it didn't "anticipate a change to our production and delivery outlook for the year."

In total, the planemaker hopes to deliver at least 400 MAXs and 70 Dreamliners this year, Reuters reported. So far, it has handed off 113 MAXs — putting it on track with its goal — but widebody output is behind with only 11 Dreamliners delivered.