United Airlines (UA) has officially become the world’s largest airline by fleet size, operating 1,000 mainline aircraft. This milestone, marked by the addition of a Boeing 737 MAX 9, cements United’s leadership in available seat miles (ASM) and global connectivity. While American Airlines (AA) and Delta Air Lines (DL) remain close competitors, United’s strategic aircraft orders and network expansion have propelled it ahead.

In 2024, United led all US carriers with 311.2 billion ASM, a 6.8% increase from 2023, surpassing both Delta (288.4 billion) and American (292.9 billion). With an average flight segment length of 1,490 miles and the most international destinations among US airlines, United continues to dominate long-haul and ultra-long-haul routes.

Despite its size, United ranks second in profitability, reporting USD 5.1 billion in operating income, behind Delta’s USD 6 billion. However, United led in revenue, recording USD 57.1 billion, narrowly surpassing Delta’s USD 57 billion. Its aggressive fleet strategy, including orders for Airbus A321neos, A321XLRs, and Boeing 737 MAX and 787 variants, ensures continued expansion.

Looking ahead, United anticipates further aircraft deliveries in 2025, strengthening its lead. While Delta and American also have expansion plans, delays in aircraft manufacturing could impact the competitive landscape. United’s focus on fleet modernisation and international growth positions it strongly to retain its dominance in the years to come.