You can find key metrics for each of the world’s top 20 airlines (based on seat capacity in 2025) in OAG’s freshly updated Takeoff report, but what do the overall data trends tell us about the current state of the aviation industry? Read on to discover the trends and key facts from Takeoff.

Overall Trends in the Top 20 Airlines

• All four of the main metrics tracked (Capacity, frequency, ASKs and routes) are growing, indicating continued post-pandemic expansion across the world’s largest carriers.
• ASK growth (+4.3% YoY) leads all metrics, and the fact that it significantly outpaces capacity growth (+2.8%) indicates that airlines are collectively flying longer sectors and prioritising long-haul expansion.
• Route growth (+2.8%) is the slowest growing metric alongside capacity for the top 20 airlines, indicating that carriers are adding capacity and frequency to existing routes more than opening new ones.
• Of the 20 airlines, 16 are growing capacity while 4 are contracting. For ASKs, 17 of 20 are growing.
• For routes, 13 airlines added routes last year, six cut, and one (ANA) is flat.
  

The Top Airlines for Key Metrics

American Airlines is the world’s largest airline by both capacity and frequency but ranks 2nd for ASKs due to its shorter domestic-heavy network.United Airlines leads on ASKs thanks to its greater long-haul exposure (22.3% international capacity vs AA’s 17.2%). Ryanair’s point-to-point model gives it the most routes despite ranking only 5th in capacity.

Fastest Growing Airlines

IndiGo, Wizz Air, and LATAM appear in the top 5 across all four growth metrics — making them the standout growth stories of 2025.

Turkish Airlines also features prominently, ranking #3 for capacity growth and #1 for frequency growth — a significant expansion year for the carrier with growth of over 7% across capacity, frequency, and ASKs.

Biggest Decliners

• Lufthansa is the biggest decliner across capacity (-4.3%), frequency (-6.9%), and ASKs (-1.4%) — the only airline shrinking on all three metrics.
• Southwest Airlines is modestly contracting in capacity (-0.9%) and frequency (-2.0%).
• Air China saw a small capacity decline of -0.8%, though its ASKs grew (+2.8%), suggesting a shift toward longer-haul routes.

How Have Airlines Recovered Since The Pandemic?

All but 5 airlines in the top 20 have surpassed their pre-pandemic 2019 capacity:

• Lufthansa: -21.7% (the furthest behind)
• All Nippon Airways: -12.8%
  Air Canada: -12.5%
• British Airways: -8.1%
• Emirates: -1.0%

The European full-service carriers and long-haul operators are notably the ones still lagging pre-pandemic levels.

These three airlines have achieved standout capacity growth since 2019:

• Wizz Air: +77.4% above 2019
• IndiGo: +67.5% above 2019
• Ryanair: +44.5% above 2019

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Which Airline Has Most Active Aircraft?

Of the top 20 airlines, United Airlines has the most active aircraft,with 1,051 in action. The combined active fleet across all 20 airlines is 9,054 aircraft (with a further 236 unavailable/in storage).

Top 5 airlines by active fleet:

1. United Airlines – 1,051
2. American Airlines – 1,016
3. Delta Air Lines – 978
4. Southwest Airlines – 803
5. China Southern Airlines – 674

Which Airline Has the Biggest Aircraft Order Book?

IndiGo has more aircraft on order than any other airline in the top 20,with 907 orders in place. Its order book equals 228% of its current active fleet of 398 aircraft. This reflects the huge growth trajectory of Indian aviation.

Total orders across all 20 airlines: 5,586 aircraft (4,611 narrow body, 954 wide body).

Top 5 airlines by aircraft orders:

1. IndiGo – 907
2. United Airlines – 674
3. Southwest Airlines – 479
4. Turkish Airlines – 369
5. Emirates – 367

(Fleet data source: ch aviation)

Average Sector Length (ASKs per Seat)

The data reveals a huge range in average sector lengths:

• Emirates leads at ~5,078 km per seat with its ultra-long-haul hub model
• Qatar Airways: ~4,650 km per seat
• British Airways: ~3,090 km

In contrast, IndiGo’s current short haul model is reflected in a ~1,164 km average sector length, and Southwest’s comes in at ~1,269 km.

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