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EmeraldSky Gold 2025: Awarded to the world's top five most emissions-efficient airlines, based on CO? per available seat kilometre (ASK).

Cirium's industry leading ranking is based on CO? per available ASK across the world's 100 largest airlines. The methodology is independently assured by PwC to ISAE 3000. It groups airlines into Gold, Silver and Bronze tiers based on global performance, which covers the top 15 airlines as well as key regional and route performers.

"Airline emissions performance comes down to decisions airlines can control - fleet choices, seat configuration and how aircraft are deployed on routes," said Jeremy Bowen, CEO of Cirium. "The airlines at the top of these rankings have got those fundamentals right, and it shows. Better emissions efficiency and lower fuel bills go hand in hand."

Scoot is the first Southeast Asian carrier to lead in global airline emissions efficiency rankings. Its average seat density of 242 seats per aircraft, operating on longer average sectors, placed it in the lead position this year. The results reinforce a consistent pattern across the industry. Airlines operating younger fleets with higher seat density continue to outperform their peers on emissions efficiency, with low-cost carriers dominating the top of the rankings. Wizz Air placed second (after placing first in 2024), followed by TUI Airways, Air Europa and Frontier Airlines, with all five carriers ranking in the top five globally and earning Gold status. Each has young fleets of aircraft compared to their peers.

-0- *T RankAirlineBase CountryPAX CO2/ASK (g)CO2 emissions (mt)Flights per Year (thousands)Fleet Age (years)Avg. distance (km)1ScootSingapore512.0656.72,1572Wizz AirHungary52.96.23354.71,5473TUI AirwaysUK53.62.2669.72,8624Air EuropaSpain53.92.169102,0235Frontier AirlinesUSA54.13.52084.81,4706TUIflyGermany54.41.65810.62,4757Virgin AtlanticUK54.52.8276.86,5668AirAsia XMalaysia54.81.620144,1779PegasusTurkey55.93.823351,37210JetstarAustralia563.718311.11,62311CondorGermany56.152.295511.22,88312Spirit AirlinesUSA56.773.782176.41,53513IberiaSpain57.034.4710011.52,83114VolarisMexico57.333.101807.51,53215IndiGoIndia57.369.847964.21,082*Gold: Ranks 1-5 | Silver: Ranks 6-10 | Bronze: Ranks 11-15. For the full list of 20 airlines, please reference the report.*T

Wizz Air remains among the strongest performers with a fleet averaging under five years, similar to other performers such as Frontier Airlines and IndiGo.

Long-haul operators, in contrast, are closing the gap primarily through fleet renewal, by removing from service older, less-fuel-efficient aircraft. Airlines such as Virgin Atlantic demonstrate that newer widebody aircraft and higher-capacity configurations can deliver competitive emissions performance even on long-distance routes.

Top Airlines by ASK

The table below reflects the top three most efficient global airlines, ranked by available seat kilometres (ASK). The top 10 global airlines as ranked by ASK, are listed in the full report.

-0- *T RankAirlineBase CountryPAX CO2/ASK (g)CO2 emissions (mt)Flights per Year (thousands)Fleet Age (years)Avg. distance (km)1Qatar AirwaysQatar60.015.419810.24,2212RyanairIreland62.717.4114810.11,2643Turkish AirlinesTürkiye64.215.84289.72,332*T

Regional and Key Intra Regional Rankings

The table below reflects regional rankings, as well as for well-trafficked corridors, the Transatlantic and Transpacific. Across every region, airlines with younger fleets and higher seat density continue to lead within their markets. Results in each region carry their own story as metrics of comparison change.

-0- *T RankAirlineBase CountryPAX CO2/ASK (g)CO2 Emissions (mt)Flights (000s)Fleet Age (yrs)Avg. Dist. (km)Intra-North America1Frontier AirlinesUSA54.53.01854.81,4022Spirit AirlinesUSA57.43.11856.51,4633WestJetCanada67.02.417511.51,348Europe1Wizz AirHungary53.13.92224.61,4622Jet2UK57.92.811013.62,2063TransaviaNetherlands59.92.011610.51,491Southeast Asia1VietJet AirVietnam64.51.41078.29412Singapore AirlinesSingapore66.70.90455.91,1813Lion AirIndonesia67.11.190.013.3828Latin America1JetSmartChile57.91.192.03.11,0332VolarisMexico58.82.01377.61,2973VivaAerobusMexico61.42.11579.11,069Transatlantic1Virgin AtlanticUK53.71.816.96.56,7592Air CanadaCanada54.92.724.414.46,1083Aer LingusIreland56.21.215.19.05,793Transpacific1Air CanadaCanada56.21.68.910.210,1782Delta Air LinesUSA57.51.911.36.19,9453Cathay PacificChina59.82.510.89.011,933*T

Airlines Closing the Gap: Capacity Growth Without Emissions Growth

Cirium's 2025 review shows whether airlines are growing capacity faster than emissions. The table below ranks individual routes by the largest year-on-year reductions in CO2 per ASK and identifies the specific aircraft transition that drove each result. To qualify, a route must have operated at least 300 round trips in the year.

The metric highlights carriers making measurable progress, not just those already operating efficient fleets. Korean Air recorded the largest long-haul route improvements globally, driven by the transition to next-generation aircraft on key transpacific routes.

-0- *T RankRouteCarrierYoY CO?/ASK ImprovementCO?/ASK 2025 (g)Fleet TransitionAvg. SeatsRoute Dist. (km)1ICN - SEAKorean Air-27.4%53.6777-300ERs ? 787-9/10s3088,3762ICN - HNLKorean Air-22.4%52.3747-8s & 777-300ERs ? 787-10s3277,3543JFK - DELAmerican Airlines-20.4%59.8777-300ERs ? 787-9s28511,7564KEF - SEAIcelandair-20.3%57.9757-200s ? A321neos1865,8105JFK - GRUAmerican Airlines-19.3%51.5777-200ERs ? 787-9s2847,6636LHR - HKGBritish Airways-18.1%64.3777/787 family ? A350-1000s3039,6317BOS - LHRDelta Air Lines-17.0%60.0A330-200s ? A330-900neos2685,2418MSP - LHRDelta Air Lines-16.9%57.2A330-200s ? A330-900neos2816,4439MUC - BOMLufthansa-16.4%55.5A340-600s ? A350-900neos2936,31210HKG - CDGCathay Pacific-16.4%62.8777-300ERs ? A350-900neos2879,590*T

"The route-level data tells a clear story," said Bowen. "When airlines swap older widebodies for next-generation aircraft, emissions per seat kilometre can fall by as much as 27 percent on that route within a year. This isn't theoretical - we're measuring it on real routes with real operational data."

About the EmeraldSky emissions report

Now in its second year, Cirium's EmeraldSky Annual Review evaluates airline emissions intensity using CO? per available seat kilometre (ASK), based on analysis of the world's 100 largest scheduled passenger airlines.

The 2025 edition also tracks year-on-year progress, measuring whether airlines are increasing capacity faster than emissions. The methodology uses flight-level operational data and is independently assured under ISAE 3000 by PwC. EmeraldSky is also accredited by the Rocky Mountain Institute as a qualified flight emissions data provider under the Pegasus Guidelines, the first climate-aligned finance framework for aviation.

About Cirium

Cirium is the world's leading aviation analytics company. It delivers aviation analytics that power decision-making for airlines, airports, travel companies, aircraft manufacturers, and financial institutions. The company provides critical and timely information, analysis, and data including airline schedules, global aircraft and fleet developments, and operational, environmental, and financial performance for companies in the sector. Cirium is part of LexisNexis Risk Solutions, a RELX business that provides information-based analytics and decision tools for professional and business customers. RELX PLC shares trade on the London, Amsterdam, and New York Stock Exchanges (ticker symbols: London: REL; Amsterdam: REN; New York: RELX).

For more information, visit cirium.com or follow Cirium on LinkedIn.

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