Singapore-based low-cost carrier Scoot has claimed the top spot as the world’s most emissions-efficient airline in Cirium’s 2025 EmeraldSky Annual Review, dethroning 2024 leader Wizz Air with just 51 grams of CO₂ per available seat kilometer (ASK).
This efficiency edge underscores the competitive advantage of low-cost carriers using younger fleets and high-density seating, enabling them to outperform larger network carriers on emissions metrics critical for regulatory compliance and cost control.
Qatar Airways ranked first among the world’s largest airlines by ASK, followed by Ryanair in second and Turkish Airlines in third, all earning recognition for superior fuel burn per seat capacity.
The global top five features low-cost dominance: Scoot (51 g CO₂/ASK), Wizz Air (52.9 g), TUI Airways (53.6 g), Air Europa (53.9 g), and Frontier Airlines (54.1 g).
Regionally, leaders include Frontier for intra-North America, Wizz Air for Europe, Virgin Atlantic for transatlantic routes, Air Canada for transpacific, JetSmart for Latin America, and Vietjet for Asia.
These rankings highlight operational strategies like modern aircraft and dense cabins as key drivers of emissions reductions, informing airline fleet investments and route planning amid rising sustainability pressures.