US Aviation Market Data Insights

Find answers to your questions about the US aviation market, with flight data insights and analysis powered by OAG's Schedules Analyser.

• Which are the top airlines in the USA?
• What's the country's busiest airport?
• Which US domestic flight route is busiest?
• Is there more domestic or international capacity in the US aviation market?
• Exclusively available to download: US monthly airline seats data from 2019-present day.

The data is updated monthly. Seats are calculated as departing seats (one-way).

• American Airlines remains the biggest carrier in the US this month with 20% of the market, 20m seats.
• Delta Air Lines and Southwest Airlines represent 19% and 18% share of the market respectively, with 18.9m and 17.9m seats in September 2025.
• As its network continues to shrink, Spirit Airlines decreased capacity again this month by 22% vs September 2024, with 863,500 fewer seats.
• Frontier Airlines also reduced capacity by 12% in September 2025.
• The Big Four - American, Delta, Southwest, and United - represent 75% of the US market in September 2025.
                                                     
• 
• 

• United Airlines led seat growth this month, adding 814,500 seats compared to September 2024. Delta Air Lines increased capacity by 282,100 compared to last year.
• Percentage-wise Breeze Airways, Cathay Pacific, and JSX increased capacity at the fastest rate of 65%, 46% and 32% respectively in September 2025.
• Breeze Airways' new route launches align with their broader success in underserved secondary markets using efficient, passenger-friendly aircraft such as the A220.
  

• The busiest route this month is New York La Guardia - Chicago O'Hare with 298,500 seats, an increase of 8% capacity vs September 2024.
• Of the Top 10 routes, Atlanta - Orlando saw the largest capacity drop this month, down 20%, followed by Honolulu - Kahului with a 12% decrease compared to September 2024.
• The Atlanta - Orlando route moved down from 7th to the 10th busiest route in September 2025.
  

• The state of Illinois saw the largest increase in seats this month, with capacity increasing by 205,800 seats vs September 2024.
• Tennessee saw the highest percentage growth in capacity this month, up 9%.
• Capacity decreased most in North Carolina again this month, by 292,400 seats, followed by California with 278,700 fewer seats vs last year.

To view US flight capacity statistics from 2019-2025, click the button below to download the data.

*As of July 2025, international capacity is reported on a two-way basis (previously one-way departing).