In a major boost for sustainable aviation, Wizz Air has claimed the top spot as the world’s most emissions-efficient airline, according to a new global benchmark released by aviation analytics firm Cirium. The Hungarian ultra-low-cost carrier leads a list of 100 global airlines, producing just 53.9 grams of CO₂ per Available Seat Kilometer (ASK), the lowest emissions intensity in the industry.
Closely following Wizz Air are Frontier Airlines (54.4g CO₂/ASK) and Turkish budget carrier Pegasus (57.1g), reflecting a broader trend: the most emissions-efficient airlines are largely low-cost carriers operating newer, high-density aircraft.
Cirium’s Flight Emissions Review aims to bring clarity and standardisation to the murky world of airline carbon reporting. Until now, comparing airline emissions has been difficult due to inconsistent methodologies and a lack of independent verification.
That has changed with Cirium’s EmeraldSky platform, the tool behind the rankings, which has achieved ISAE 3000 Reasonable Assurance from Price water house Coopers and recognition from the Rocky Mountain Institute. The platform calculates emissions intensity using aircraft-level operational data, including seating density, fleet age, and route specifics.
“EmeraldSky provides the industry-standard benchmark that enables fair comparison and meaningful progress tracking,” said Jeremy Bowen, CEO of Cirium. “For the first time, airlines can measure emissions performance on equal terms using trusted, verified data.”
Wizz Air’s top ranking is attributed to its young, all-Airbus fleet, with many aircraft configured with 239 or more seats, helping spread emissions across more passengers. Its average fleet age sits at just 5.1 years. Frontier and Pegasus follow similar strategies, operating efficient aircraft with dense layouts.
Top 5 Airlines by Lowest CO₂ per ASK:
| Rank | Airline | CO₂ / ASK (g) | Avg. Seats | Avg. Fleet Age |
|---|---|---|---|---|
| 1 | Wizz Air | 53.9 | 222 | 5.1 years |
| 2 | Frontier Airlines | 54.4 | 204 | 4.5 years |
| 3 | Pegasus Airlines | 57.1 | 209 | 4.5 years |
| 4 | Volaris | 57.9 | 196 | 6.9 years |
| 5 | IndiGo | 58.2 | 181 | 4.1 years |
What unites these carriers is their commitment to efficiency: high-density seating, modern fleets, and streamlined operations, all crucial in lowering emissions per passenger kilometre.
Cirium also evaluated the ten largest airlines by seat capacity to assess how scale influences sustainability. Among these giants, Ryanair emerged as the most emissions-efficient, producing 63.0g of CO₂ per ASK, significantly ahead of U.S. legacy carriers.
However, scale comes at a cost. Ryanair, despite its relative efficiency, remains Europe’s top polluting airline by total emissions, producing over 15 million metric tonnes of CO₂ in 2023, more than seven million petrol cars combined.
The largest airlines by lowest CO₂ per ASK:
| Rank | Airline | CO₂ / ASK (g) | Avg. Fleet Age |
|---|---|---|---|
| 1 | Ryanair | 63.0 | 9.1 years |
| 2 | Southwest | 68.9 | 11.9 years |
| 3 | Delta Air Lines | 74.4 | 15.1 years |
| 4 | American Airlines | 74.6 | 13.8 years |
| 5 | United Airlines | 75.4 | 15.7 years |
Legacy carriers tend to operate mixed fleets, with older wide-body jets and premium-heavy configurations, pushing their emissions per ASK higher.
Despite the challenges, many airlines, including Ryanair, have committed to reaching net-zero emissions by 2050. Strategies include increasing use of sustainable aviation fuels (SAFs), new aircraft technologies, carbon offsets, and more efficient air traffic systems like the Single European Sky ATM Research (SESAR) initiative.
Ryanair’s breakdown of its 2050 sustainability roadmap:
- 34% emissions reduction via SAF
- 32% through technology & operations
- 24% via offsets and other mechanisms
- 10% from improved air traffic management
Cirium’s rankings mark a pivotal moment for the aviation sector, offering transparent, comparable metrics in an industry often criticised for opaque sustainability claims. As regulators, investors, and travellers increasingly demand climate accountability, tools like EmeraldSky could become essential for shaping airline reputations and investment decisions.
For Wizz Air, the recognition cements its status not just as a low-cost leader but as a model for emissions efficiency in commercial aviation’s climate-conscious future.