United Airlines Leads with the World’s Largest Mainline Fleet in 2025

United Airlines has emerged as the airline with the largest mainline fleet in the world as of 2025, according to data from ch-aviation. This designation of “mainline” refers specifically to aircraft operated directly by the airline, excluding those contracted to partners or regional subsidiaries. With a fleet exceeding 1,056 aircraft and nearly 250,000 seats available, United Airlines stands at the forefront of the aviation industry.

United Airlines: A Closer Look at the Fleet

United’s expansive fleet is characterized by a diverse range of aircraft. The most numerous widebody jets in its lineup are the Boeing 777-200ER, of which the airline operates 55 units. In stark contrast, United’s narrowbody jets dominate its fleet composition, featuring four variants of the Boeing 737 series, each with over 100 examples. These include the 737-800 and 737-900ER, along with the newer MAX 8 and MAX 9 models.

The following table summarizes the top widebody and narrowbody aircraft within United Airlines’ fleet:

Overall, United Airlines’ mainline fleet boasts an average age of 16.9 years and a total capacity of 238,225. In stark contrast to its current holdings, the airline has also phased out several older models, including 101 Boeing 737-300s and 84 737-500s.

Competitors: American Airlines and Delta Air Lines

Following closely behind United are American Airlines and Delta Air Lines, with mainline fleets of 1,001 and 1,010 aircraft, respectively. Delta’s fleet is similarly focused on narrowbody jets, with a significant number of Airbus A321s supplementing its operations. The airline currently operates 158 Boeing 737-900ERs and a collection of smaller widebody jets, including 39 Airbus A330-900s.

Here is a breakdown of Delta Air Lines’ fleet:

American Airlines has a strong presence in the narrowbody market, with a fleet dominated by 303 Boeing 737-800s and 218 Airbus A321-200s, while its widebody fleet comprises various models of Boeing jets.

As the competition intensifies, both American and Delta have substantial order sheets to expand their fleets, with American Airlines committing to 300 new aircraft, including over a third designated as Boeing 737 MAX.

Future Outlook for United Airlines

United Airlines is set to reinforce its leading position with an extensive order book of 666 aircraft pending delivery. This commitment is largely attributed to the aging of its current fleet, which necessitates a phased replacement of older models. Notably, the airline has placed significant orders for 167 Boeing 737 MAX 10s, with expectations for delivery beginning in 2027 or 2028.

Andrew Nocella, Chief Commercial Officer of United Airlines, emphasized the importance of timely aircraft delivery to maintain operational efficiency. In a recent statement, he noted that while the airline has committed to the MAX 9 as a stopgap, they anticipate the MAX 10 to enhance their fleet capabilities once certified.

Despite this ambitious expansion plan, United has opted not to include the Boeing 777X in its future acquisitions. The decision aligns with the airline’s strategy to focus on more efficient, smaller aircraft, as highlighted by Patrick Quayle, Senior Vice President of Global Network Planning and Alliances.

Flight Operations and Market Reach

In 2024, United Airlines scheduled approximately 1.6 million flights across its extensive network. The airline serves a wide range of 944 routes in May alone, predominantly within the United States. The busiest domestic route connects Chicago to LaGuardia, with an average of 14 flights daily.

On the international front, United operates 283 routes to destinations beyond the United States, including 122 international locations. Toronto Pearson International Airport ranks as the busiest international destination, followed closely by London Heathrow Airport, underscoring United’s robust global presence.

As United Airlines continues to evolve and expand, it remains a key player in the international aviation landscape, setting benchmarks for fleet size and operational capacity.