United Airlines, one of Boeing's largest customers, is reconsidering its fleet expansion plans involving the Boeing 737 Max 10, as expressed by CEO Scott Kirby. The airline's decision comes amid continued delays in the certification of the Max 10 and recent grounding of the 737 Max 9 variant, which has significantly impacted United's operations and financial outlook.

In a recent interview on CNBC's "Squawk Box," Kirby expressed his frustration over Boeing's manufacturing challenges, especially after the January 5 incident where a door plug blew out during an Alaska Airlines 737 Max 9 flight, leading to the FAA grounding the planes. United Airlines, which operates 79 of these aircraft, anticipates a first-quarter loss due to the ongoing grounding. "I think the Max 9 grounding is probably the straw that broke the camel's back for us," Kirby stated, hinting at a strategic shift away from the Max 10.

Back in 2018, United had high hopes for the Max 10s, with Kirby, then the airline's president, outlining cabin plans for about 100 Max 10s they had ordered, aiming to fly them in 2020. These planes were expected to replace older jets in the fleet. However, the repeated delays and recent issues have led to a reevaluation of these plans.

Kirby's comments contrast sharply with those of Delta Air Lines CEO Ed Bastian, who remains confident in moving forward with Boeing Max 10 orders. Boeing, on its part, has not commented specifically on the Max 10 situation. Still, Stan Deal, Boeing's CEO of commercial airplanes, has acknowledged the company's challenges and expressed commitment to resolving them.

In a broader context, United's potential shift away from the Max 10 reflects deepening concerns over Boeing's manufacturing and quality control issues. These challenges have plagued the aerospace giant, delaying deliveries and affecting its reputation in the industry. Kirby's remarks signal a possible pivot towards other aircraft manufacturers, notably Airbus, Boeing's main competitor.

The implications of this decision extend beyond United Airlines. If one of Boeing's key customers moves away from the Max 10, it could signal wider industry skepticism about Boeing's ability to deliver on its commitments and maintain the high quality and safety standards expected in aviation. This scenario could result in slower growth for United, as Kirby acknowledged, but also represents a significant moment of introspection for Boeing as it strives to restore trust with its airline partners.