According to the U.S. Department of Transportation's recent data, United Airlines was the leading carrier at Chicago O'Hare International Airport between February 2024 and January 2025. During this period, United Airlines, together with its regional arm United Express, moved 37.08 million two-way passengers. This resulted in O'Hare airport being United's second-busiest hub after Denver.
"United was so dominant at O'Hare that it provided nearly one in two passengers," notes the Department of Transportation. United's passenger traffic increased by nearly 2% compared to the pre-pandemic period of February 2019 to January 2020, despite the fact that overall airport throughput remained lower. The airport is not considered a fortress hub due to the strong presence of other major airlines like American.
In addition to the dominance of United Airlines at O'Hare, the top ten airlines accounted for nearly 90% of the airport's passenger traffic during this timeframe. Spirit Airlines, the third-largest operator at O'Hare, significantly contributed with 21 nonstop routes. "Spirit transported more passengers to/from Fort Lauderdale—the airline's most-served airport networkwide—than anywhere else," highlighting its strong point-to-point market leading position.