New Rankings Highlight Airlines Leading Emissions Efficiency Race

by Mia Taylor
Last updated: 2:20 PM ET, Wed July 2, 2025

Budget carrier Wizz Air has just proved that operating an ultra low cost business doesn’t require sacrificing environmental standards.

The Hungarian-based carrier has just been named the world’s most emissions-efficient airline for 2024, according to a new ranking released today by the aviation analytics company Cirium.

The Cirium Flight Emissions Review ranks the top 20 airlines globally with regard to their flight emissions and found that Wizz Air emits an industry low of 53.9 grams of CO₂ per Available Seat Kilometer (ASK).

Wizz Air is merely one example of budget carriers leading the way in the aviation industry with regard to cutting CO2.

The second place slot in the ranking is held by yet another budget carrier, USA-based Frontier Airlines Frontier Airlines, with emissions of 54.4 grams. Rounding out the top three airlines in the ranking is Turkey’s low-cost carrier Pegasus with emissions of 57.1 grams, according to the report. 

What’s more, all of the top 10 airlines globally with the lowest emissions are budget carriers.

The ranking is developed based on verified, comparable data and provides an important gauge of the aviation industry’s progress toward its goal of achieving Net Zero by 2050.

Each airline’s performance is generated using Cirium’s EmeraldSky platform, which has been vetted and achieved ISAE 3000 Reasonable Assurance from PricewaterhouseCoopers (PwC) and official accreditation from the Rocky Mountain Institute (RMI).

Here’s a closer look at the top 10 ranked airlines, meaning the airlines with the lowest carbon emissions globally (along with their emissions data per ASK).

• Wizz Air: 53.9
• Frontier Airlines: 54.
• Pegasus: 57.1
• Volaris: 57.9
• IndiGo: 58.2
• Jetstar: 58.4
• Spirit Airlines: 58.4
• Scoot: 58.7
• SunExpress: 59.4
• Air India Express: 60.5
  
  

The CO2 Emissions of Largest Airlines in the World

Cirium’s reporting also ranked the 10 largest airlines in the world by ASK. Leading the pack in this category when it comes to the emissions-cutting efforts is Ryanair, followed by Southwest Airlines and Delta Air Lines.

Each of the major carriers in the United States earned a spot among the top 10, while Turkish Airlines, Qatar Airlines and Emirates rounded out a group of primarily long-haul operators. 

Here’s a closer look at the ranking of the world’s largest carriers and their emissions by ASK.

• Ryanair: 63.0
• Southwest Airlines: 68.9
• Delta Air Lines: 74.4
• American Airlines: 74.6
• United Airlines: 75.4
• Turkish Airlines: 76.9
• China Southern Airlines: 78.2
• Qatar Airways: 79.7
• Air China: 83.3
• Emirates: 84.9

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