Scoot, Qatar, and Ryanair Top Cirium Global Airline Emissions Rankings in 2025

Singapore-based Scoot has been named the world’s most emissions-efficient airline in Cirium’s 2025 EmeraldSky Annual Review, taking the top position from last year’s leader, Wizz Air. Qatar Airways, Ryanair, and Turkish Airlines were each recognized as the top three most efficient global airlines, ranked by available seat kilometres (ASK).

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Cirium’s industry leading ranking is based on CO₂ 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.

Rank	Airline	Base Country	PAX CO2/ASK (g)	CO2 emissions (mt)	Flights per Year (thousands)	Fleet Age (years)	Avg. distance (km)
1	Scoot	Singapore	51	2.0	65	6.7	2,157
2	Wizz Air	Hungary	52.9	6.2	335	4.7	1,547
3	TUI Airways	UK	53.6	2.2	66	9.7	2,862
4	Air Europa	Spain	53.9	2.1	69	10	2,023
5	Frontier Airlines	USA	54.1	3.5	208	4.8	1,470
6	TUIfly	Germany	54.4	1.6	58	10.6	2,475
7	Virgin Atlantic	UK	54.5	2.8	27	6.8	6,566
8	AirAsia X	Malaysia	54.8	1.6	20	14	4,177
9	Pegasus	Turkey	55.9	3.8	233	5	1,372
10	Jetstar	Australia	56	3.7	183	11.1	1,623
11	Condor	Germany	56.15	2.29	55	11.2	2,883
12	Spirit Airlines	USA	56.77	3.78	217	6.4	1,535
13	Iberia	Spain	57.03	4.47	100	11.5	2,831
14	Volaris	Mexico	57.33	3.10	180	7.5	1,532
15	IndiGo	India	57.36	9.84	796	4.2	1,082
*Gold: Ranks 1-5 | Silver: Ranks 6-10 | Bronze: Ranks 11-15. For the full list of 20 airlines, please reference the report.

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.

Rank	Airline	Base Country	PAX CO2/ASK (g)	CO2 emissions (mt)	Flights per Year (thousands)	Fleet Age (years)	Avg. distance (km)
1	Qatar Airways	Qatar	60.0	15.4	198	10.2	4,221
2	Ryanair	Ireland	62.7	17.4	1148	10.1	1,264
3	Turkish Airlines	Türkiye	64.2	15.8	428	9.7	2,332

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.

Rank	Airline	Base Country	PAX CO2/ASK (g)	CO2 Emissions (mt)	Flights (000s)	Fleet Age (yrs)	Avg. Dist. (km)
Intra-North America
1	Frontier Airlines	USA	54.5	3.0	185	4.8	1,402
2	Spirit Airlines	USA	57.4	3.1	185	6.5	1,463
3	WestJet	Canada	67.0	2.4	175	11.5	1,348
Europe
1	Wizz Air	Hungary	53.1	3.9	222	4.6	1,462
2	Jet2	UK	57.9	2.8	110	13.6	2,206
3	Transavia	Netherlands	59.9	2.0	116	10.5	1,491
Southeast Asia
1	VietJet Air	Vietnam	64.5	1.4	107	8.2	941
2	Singapore Airlines	Singapore	66.7	0.90	45	5.9	1,181
3	Lion Air	Indonesia	67.1	1.1	90.0	13.3	828
Latin America
1	JetSmart	Chile	57.9	1.1	92.0	3.1	1,033
2	Volaris	Mexico	58.8	2.0	137	7.6	1,297
3	VivaAerobus	Mexico	61.4	2.1	157	9.1	1,069
Transatlantic
1	Virgin Atlantic	UK	53.7	1.8	16.9	6.5	6,759
2	Air Canada	Canada	54.9	2.7	24.4	14.4	6,108
3	Aer Lingus	Ireland	56.2	1.2	15.1	9.0	5,793
Transpacific
1	Air Canada	Canada	56.2	1.6	8.9	10.2	10,178
2	Delta Air Lines	USA	57.5	1.9	11.3	6.1	9,945
3	Cathay Pacific	China	59.8	2.5	10.8	9.0	11,933

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.

Rank	Route	Carrier	YoY CO₂/ASK Improvement	CO₂/ASK 2025 (g)	Fleet Transition	Avg. Seats	Route Dist. (km)
1	ICN – SEA	Korean Air	-27.4%	53.6	777-300ERs → 787-9/10s	308	8,376
2	ICN – HNL	Korean Air	-22.4%	52.3	747-8s & 777-300ERs → 787-10s	327	7,354
3	JFK – DEL	American Airlines	-20.4%	59.8	777-300ERs → 787-9s	285	11,756
4	KEF – SEA	Icelandair	-20.3%	57.9	757-200s → A321neos	186	5,810
5	JFK – GRU	American Airlines	-19.3%	51.5	777-200ERs → 787-9s	284	7,663
6	LHR – HKG	British Airways	-18.1%	64.3	777/787 family → A350-1000s	303	9,631
7	BOS – LHR	Delta Air Lines	-17.0%	60.0	A330-200s → A330-900neos	268	5,241
8	MSP – LHR	Delta Air Lines	-16.9%	57.2	A330-200s → A330-900neos	281	6,443
9	MUC – BOM	Lufthansa	-16.4%	55.5	A340-600s → A350-900neos	293	6,312
10	HKG – CDG	Cathay Pacific	-16.4%	62.8	777-300ERs → A350-900neos	287	9,590

"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 CO₂ 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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