United Airlines (UA, Chicago O'Hare) does not expect to take delivery of its first B737-10 before 2027 or 2028, due to uncertainty regarding the aircraft's certification, CCO Andrew Nocella said on May 13 during a company event in New York. As quoted by Reuters, Nocella commented that United might no longer be the first airline to introduce the biggest MAX variant to its fleet.

While the carrier waits for the delivery of its B737-10s, it will continue taking smaller B737-9s as it aims to modernise its fleet. "We want to see the aircraft [B737-10] certified before we make the firm commitment to convert our -9s to -10s," Nocella said.

According to the ch-aviation Commercial Aviation Aircraft Data module, United Airlines has unfulfilled orders for 165 B737-10s, making it the largest customer for the type in the world. Its 2024 annual report reveals it was expecting to receive its first three -10s by the end of 2026.

The American carrier initially anticipated taking the first B737-10 in 2020. Due to the grounding of the MAX aircraft family and certification delays, both with the B737-10 and the smaller B737-7 variant, the deliveries have slipped into the second half of this decade.

The airline remains hopeful that Boeing will manage to overcome the certification issues and deliver the B737-10. In January 2025, United's chief financial officer, Mike Leskinen, said the company had become more bullish on the B737-10s as the manufacturer was improving its business.

United Airlines is already relying on a sizeable MAX fleet, with 118 B737-8s and ninety-nine B737-9s currently operating in its network. It finished the first quarter of 2025 with 209 MAX aircraft in its fleet, nine more than it previously anticipated in its investor update released on January 21, 2025.

Despite the improved outlook on new aircraft arrivals, the current delivery timeline is still below United's previous expectations. The company revealed that it had contractually agreed with Boeing to receive sixty-seven MAX jets in the second, third, and fourth quarters of 2025, but will only add twenty-seven aircraft. United Airlines is now looking to finish 2025 with 236 MAX family aircraft.

The carrier has also changed its delivery timeline for the long-awaited A321-200NY(XLR)s. In its 2024 annual report, the airline noted it had twelve A321XLRs contractually due in 2026 but only expected nine. However, the most recent quarterly update indicates that it will receive eight by the end of 2026, in line with an adjusted contractual timeline. The company has fifty A321XLRs on order from Airbus.