The top 20 Major airlines globally, ranked by lowest CO2/ASKThe world's largest airlines, ranked by lowest CO2/ASK

Cirium, the aviation analytics company, creates a new transparent standard and ranking for airline CO2 emissions, identifying the best performing airlines in specific categories

LONDON, July 02, 2025--(BUSINESS WIRE)--Wizz Air is the world's most emissions-efficient airline in new rankings released today by Cirium, the aviation analytics firm. The Cirium Flight Emissions Review ranks the top 20 airlines globally, through a consistent benchmark for flight emissions.

Wizz Air, the Hungary-based ultra-low-cost airline emits an industry low of 53.9 grams of CO₂ per Available Seat Kilometer (ASK)*, followed by Frontier Airlines (54.4 grams) and Pegasus (57.1 grams) according to the report.

The rankings provide the aviation industry with verified comparable data on an equal playing field as the sector advances toward Net Zero by 2050 commitments. The rankings performance use Cirium's EmeraldSky platform, which achieved ISAE 3000 Reasonable Assurance from PricewaterhouseCoopers (PwC) and official accreditation from the Rocky Mountain Institute (RMI).

Wizz Air, Frontier, and Pegasus Top 3; The Top 20 Major Airlines Ranked by CO2 Emissions/ASK

The top 20 Major airlines globally are presented in the corresponding tables.

Of note is the performance of Indigo, top in Asia, Volaris, top in Latin America and the Caribbean, and Jetstar, for its performance in Australia.

The CO2/ASK Emissions of the World’s Largest Airlines

Cirium’s reporting also ranked the 10 largest airlines in the world by ASK. At the head of the table is Ryanair, followed by Southwest Airlines, and Delta Air Lines. Each of the major U.S. carriers earned spots at the table, while Turkish Airlines, Qatar Airlines and Emirates rounded out a group of primarily long-haul operators.

Enabling Fair Comparison Across the Industry

"For the first time, airlines can compare their emissions performance using a consistent, verified methodology," said Jeremy Bowen, CEO at Cirium. "EmeraldSky provides the industry-standard benchmark that enables fair comparison and meaningful progress tracking."

The comprehensive Review analyzed global operations using dual-accredited methodology, with the full report containing extensive findings across:

Global Category Rankings showing the top 20 Major airlines and the World’s 10 largest airlines by CO₂ per Available Seat Kilometer Regional Performance breakdowns showing which airlines excel on intra-region and inter-region routes Route-Level Improvements identifying specific airport pairs with the greatest efficiency gains Operational Insights revealing how fleet composition, load factors, and route optimization drive performance differences

Story Continues

The Review provides comprehensive operational insights that support industry-wide efficiency improvements, offering actionable intelligence for aviation stakeholders committed to sustainability progress.

Setting New Industry Transparency Standards

EmeraldSky's methodology achieved the highest level of assurance under International Standard on Assurance Engagements through rigorous independent review. The Rocky Mountain Institute's accreditation under the Pegasus Guidelines validates the approach for climate-aligned aviation financing, enabling banks and investors to make informed decisions based on verified emissions data.

This standardized approach addresses aviation's fragmented sustainability reporting, where inconsistent methodologies have made meaningful comparisons impossible. The verified benchmark enables airlines to assess their operational efficiency accurately, investors to evaluate performance reliably, and corporations to report Scope 3 emissions with confidence.

Quarterly Updates Drive Accountability

The Flight Emissions Review will be updated quarterly, tracking performance changes and operational improvements across the industry. With hundreds of data points and detailed analysis across multiple categories, the report provides the most comprehensive view of aviation emissions performance available.

Access the Complete Rankings and Analysis

The full Flight Emissions Review, including detailed carrier rankings, regional breakdowns, route-specific analysis, and operational insights, is available for download at www.cirium.com/flight-emissions-review.

Notes to Editors

* Available Seat Kilometers (ASK) is a metric in the airline industry that represents the total passenger capacity of an airline

About Cirium

Cirium® is the world’s most trusted source of aviation analytics. The company delivers powerful data and cutting-edge analytics to empower a wide spectrum of industry players. It equips airlines, airports, travel enterprises, aircraft manufacturers, and financial entities with the clarity and intelligence they need to optimize their operations, make informed decisions, and accelerate revenue growth.

Cirium® is part of LexisNexis® Risk Solutions, a RELX business, which provides information-based analytics and decision tools for professional and business customers. The shares of RELX PLC are traded on the London, Amsterdam and New York Stock Exchanges using the following ticker symbols: London: REL; Amsterdam: REN; New York: RELX.

Download the complete Flight Emissions Review with full rankings, regional analysis, and operational insights at www.cirium.com/flight-emissions-review

View source version on businesswire.com: https://www.businesswire.com/news/home/20250702342529/en/

Contacts

Media Contact:
Mike Arnot, Cirium spokesperson
[email protected] 
+1 (212) 518-4796

Callum McGoldrick
[email protected] 
+44 (784) 2971398

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