What were the biggest aviation milestones of 2025, and what do they signal for the year ahead? From the busiest day for global air capacity to routes operating more than 100 flights a day, plus the fastest-growing airlines and the airports expanding their networks, our data provides the answers.
As a leading provider of air travel data to the global travel industry, OAG brings together the key statistics that defined 2025 and set the scene for 2026.
Which was the busiest day for AIR CAPACITY in 2025?
On Friday August 1st, global airline seat capacity reached 19,833,642*, making this the busiest day of the year for air travel, and surpassing 2024's busiest day by over 555,000 seats.
Which was the quietest day for air travel in 2025?
The lowest daily global airline capacity figure recorded in 2025 was on Tuesday 28th January; 15,200,778* seats were scheduled. You can find out more about the patterns we see in the busiest and quietest days for air travel by reading our analysis here.
Top Airlines of 2025
The top airlines of 2025 vary depending on which metric you choose!
When we rank airlines by the number of seats operated:
- American Airlines comes out on top with 279.6 million seats.
- The rest of the top four airlines based on annual seats are the remaining big four US airlines:
- Delta (246.9M seats)
- Southwest (229.2M seats)
- United Airlines (225.5M seats)
- Rounding out the top five is Ryanair with 213.1M seats.
There is a slight variation when the world's top airlines are ranked by frequency ie. total number of flights. Here, American Airlines comes out on top but the other US airlines shuffle positions:
- American Airlines - 2.3M flights
- Delta Airlines - 1.8M flights
- United Airlines - 1.7M flights
- Southwest Airlines - 1.4M flights
- Ryanair - 1.1M flights
Another key metric for airlines is Available Seat Kilometres (ASKs), and when we rank by ASKs, United Airlines comes out on top:
- United Airlines - 536.5bn ASKs
- American Airlines - 487.9bn ASKs
- Delta Airlines - 483.7bn ASKs
- Emirates - 380.6bn ASKs
- Southwest - 290.8bn ASKs
Which Airport added most routes in 2025?
The airport that added the most routes in 2025 was Hong Kong (HKG), where 24 new routes operated compared to 2024. Cathay Pacific, HK Express, United Airlines and Hong Kong Airlines all added significant routes to boost connectivity.
Airline Routes with more than 100 flights per day
In 2025, eight routes had an average daily frequency of 100 flights or more - that's four or more flights per hour! These routes, listed below along with their average daily frequency in 2024, are among the busiest domestic routes in the world.
- CJU-GMP, 194 flights per day
- MEL-SYD, 134 flights per day
- JED-RUH, 130 flights per day
- HAN-SGN, 123 flights per day
- FUK-HND, 113 flights per day
- CTS-HND, 109 flights per day
- BOM-DEL, 107 flights per day
- CGH-SDU, 103 flights per day
The Fastest Growing Airline of 2025
Colombian ATR (regional aircraft) operator Clic Air grew capacity by 50% in 2025, making it the fastest-growing airline of the year. An increase in flight frequency on the popular Bogata - Medellin route (now 10 per day) is a large contributor to this growth.
The fastest growing airport by Seats is...
As well as adding most routes, Hong Kong airport has added most seats this year. This growth has been enabled by infrastructure expansion; in 2025 the airport's three runways were able to operate concurrently for the first time.
*This number includes stopping flights.
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