US aviation market data

US aviation market at a glance

Here are some highlights from this month's US market data:

• Largest airline: American Airlines (22.4m seats)
• Busiest airport: Atlanta Hartsfield-Jackson (5.4m seats)
• Busiest US domestic flight route: Denver to Phoenix (322,100 seats)
• State adding most airline capacity: Illinois (+683,700 seats)

Top 10 biggest US airlines by seats

• The Big Four (American Airlines, Delta Air Lines, United Airlines, and Southwest Airlines) represent 74% share of the market in March 2026.
  
• American Airlines remains the biggest carrier in the US in March 2026 with 21% of the market, operating 22.4m seats.
• Southwest Airlines holds a 19% market share with 19.8 million seats, while Delta Air Lines holds 18% with 19.6 million seats.
• Spirit Airlines has decreased capacity by 32% year-on-year with 1.2m fewer seats.

Top 10 US airlines adding capacity year on year

• United Airlines added the most seats this month, increasing seats by 800,400 vs March 2025.
• American Airlines made the second largest capacity increase of 631,000 seats vs last year.
• Percentage-wise, Breeze continues to increase capacity at the fastest rate of 41% year-on-year, followed by Avianca with 14% more capacity. 

Top 10 busiest airline routes in the US

• The busiest airline route in the US in March 2026 is Denver to Phoenix with 322,100 seats, despite a decline in capacity of 3% year-on-year.
• Atlanta to Fort Lauderdale is the second busiest route with 308,600 seats, an increase of 31% capacity vs March 2025.
• The Orlando to Chicago route recorded the largest percentage increase of 34%, an additional 67,100 seats.
• Capacity decreased most again on the Honolulu to Kahului route, by 12%, followed by Las Vegas to Los Angeles declining by 11% vs March 2025.

Top 10 busiest US airports

Top 10 airports by departing seats (one-way) this month 

• Atlanta remains the biggest airport in capacity terms, with 5.4m seats - 5% share of capacity.
• Chicago O’Hare recorded the largest capacity growth again this month, adding 608,400 seats year on year to reach 4.6 million seats. As highlighted in our recent blog, major global carriers United Airlines and American Airlines are driving this increase, with United growing to 2.2 million seats and American to 1.6 million seats in March 2025. 
• Las Vegas decreased capacity most within the Top 10 again this month, with 243,000 fewer seats year on year.

US states adding & removing most capacity this month vs same month last year

• Illinois saw the largest capacity growth in March 2026, adding 683,700 seats year-on-year. Florida recorded the second-largest increase, with 233,700 additional seats compared with March 2025.
• Illinois recorded the strongest percentage growth in capacity, up 13.2%, followed by Oregon with a 10.1% increase this month.
• Nevada recorded the largest capacity decline this month, with 232,500 fewer seats than last year, followed by California, down 178,400 seats year-on-year.

Total US flight capacity by month, domestic & international

To view US flight capacity statistics from 2019-2026, 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).

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