United Airlines holds largest global airline fleet as U.S.-based carriers dominate rankings

Delta Air Lines holds third place with a fleet size of 992 aircraft. Operating since 1928 and based at Hartsfield-Jackson Atlanta International Airport—one of the busiest airports globally—Delta serves over 325 destinations across more than fifty countries. Delta operates a diverse mix of Boeing and Airbus models through seven subsidiaries such as Delta Connection and Endeavor Air. The average age of its fleet is around fifteen years; Delta currently has eleven new aircraft on order.

Southwest Airlines is fourth by fleet size with a total of 798 all-Boeing-737 aircraft. Established in 1967 with headquarters at Dallas Love Field Airport, Southwest maintains one type to simplify maintenance but limits range options compared to competitors operating varied fleets. Of its current orders for forty-four new Boeing jets, certification delays have affected some deliveries.

While United leads in sheer number of planes, other measures paint a nuanced picture among these carriers:

- American Airlines has the highest market share for available seats.

- Delta Air Lines leads both brand revenue value and overall revenue.

- Southwest remains the largest low-cost carrier by network size—operating over three thousand routes—and carries the most passengers among these four airlines.

- According to OAG data, these four airlines represent seventy-four percent of all U.S. airline seats—a combined total of five hundred thirty-eight million seats annually.

“In terms of passenger popularity, Delta Air Lines is considered the most valuable and the most reliable airline,” states the analysis. “In comparison, American Airlines has a large fleet but passengers report more delays and cases of mishandled baggage.”

Market share measured by Revenue Passenger Miles shows Delta ahead; seat capacity figures give American twenty-one percent market share followed by Delta at nineteen percent; Southwest holds eighteen percent; United follows closely at sixteen percent.

The competition among these major U.S.-based airlines remains close not only in terms of numbers but also regarding perceived value to customers, reliability metrics, route networks, and expansion plans.

“As we can see, there are numerous aspects to what makes an airline the largest or best in the world,” notes the report. “Although United Airlines is the leader...in terms of actual fleet size, the numbers are quite close when comparing number of seats and market share.”

Whether United will maintain its lead or be overtaken depends on evolving strategies within this competitive sector.