Scoot, Qatar and Ryanair will top Cirium |’s global emissions rankings in 2025 News
Singapore-based Scoot has been named the world’s most emissions-efficient airline in Cirium’s EmeraldSky Annual Review 2025, taking the top spot from last year’s leader, Wizz Air. Qatar Airways, Ryanair and Turkish Airlines were each recognized as the three most efficient airlines, ranked by available seat kilometers (ASK).
Cirium’s industry-leading ranking is based on CO₂ per available ASK across the world’s 100 largest airlines. The methodology is independently guaranteed by PwC to ISAE 3000. It groups airlines into Gold, Silver and Bronze levels based on global performance, which includes the top 15 airlines as well as key regional and route performers.
“Airline emissions performance comes down to decisions that airlines can control – fleet choices, seat configuration and how aircraft are deployed on routes,” said Cirium CEO Jeremy Bowen. “The airlines at the top of this ranking have got the basics right, and it shows. Better emissions efficiency and lower fuel bills go hand in hand.”
Scoot is the first Southeast Asian airline to lead the global airline emissions efficiency rankings. Its average seat density of 242 seats per aircraft, operating in longer average sectors, placed it in the leading position this year. The results reinforce a consistent pattern across the sector. Airlines operating younger fleets with higher seat densities continue to outperform their competitors in terms of emissions efficiency, with low-cost airlines dominating the top of the rankings. Wizz Air came in second (after first place in 2024), followed by TUI Airways, Air Europa and Frontier Airlines, with all five airlines ranking in the top five worldwide and earning Gold status. They all have a young fleet of aircraft compared to their peers.
Wizz Air remains one of the strongest performers with an average fleet life of less than five years, comparable to other performers such as Frontier Airlines and IndiGo.
Long-haul operators, on the other hand, are closing the gap mainly through fleet renewal, by retiring older, less fuel-efficient aircraft. Airlines such as Virgin Atlantic are showing that newer widebody aircraft and higher capacity configurations can deliver competitive emissions performance, even on long-haul routes.
Cirium’s 2025 evaluation shows whether airlines are growing their capacity faster than their emissions. The table below ranks the individual routes by the largest annual CO2 reductions per ASK and identifies the specific aircraft transition that led to each result. To be eligible, a route must have operated at least 300 round trips in the year.
The metric highlights those carriers that are making measurable progress, not just those that already operate an efficient fleet. Korean Air recorded the largest improvements globally in long-haul routes, driven by the transition to next-generation aircraft on key trans-Pacific routes.
“The route-level data tells a clear story,” says Bowen. “If airlines swap older widebodies for next-generation aircraft, emissions per seat kilometer could drop by as much as 27 percent on that route within a year. This is not theoretical: we measure it on real routes with real operational data.”
