Airline Sustainability Rankings

Ranking Methodology

No single universally agreed ranking for airline sustainability exists — different indices prioritise different metrics, leading to conflicting conclusions. The main methodologies are:

• Atmosfair Airline Index: Measures CO2 per passenger-kilometre using actual fuel consumption and seating configuration data submitted by airlines; updated annually; covers ~200 airlines
• ICCT Global Aviation Carbon Index: Uses ICAO fuel burn data; focuses on per-seat fuel intensity rather than per-passenger efficiency, making it independent of load factor gaming
• CDP Climate disclosure: Evaluates comprehensiveness and quality of climate reporting; does not rank by emissions intensity but by transparency and governance
• Sustainalytics / MSCI ESG scores: Investor-focused; incorporate governance, lobbying activity, and policy positions alongside emissions data

The most robust approach is to look at a combination of verified fuel intensity data (Atmosfair or ICCT) and voluntary reporting quality (CDP).

Top Performing Airlines (2024)

Based on grams of CO2 per revenue passenger-kilometre (RPK), the most efficient major carriers globally are consistently from the low-cost European and Asian sectors:

• Wizz Air: Consistently ranks among the lowest CO2/pkm globally — ~60–65 g CO2/pkm; high-density seating, young A320neo/A321neo fleet, high load factors
• Ryanair: ~65–70 g CO2/pkm; similar model to Wizz Air; but has faced criticism for lobbying against carbon pricing
• easyJet: ~73 g CO2/pkm; significant A320neo fleet; publicly committed to net zero by 2050 with interim targets
• IndiGo (India): Large fleet of A320neos; high load factors on dense Indian routes; efficient per-seat metric
• Korean Air: Top performer among full-service long-haul carriers; early 787 adopter; rigorous fuel monitoring programme

SAF Usage as a Differentiator

Per-seat efficiency metrics favour high-density low-cost carriers whose model has little to do with sustainability investment. SAF usage is a more intentional metric: airlines choosing to pay a premium for lower-carbon fuel are making active sustainability investments. Top SAF users in 2023–2024 include United Airlines (largest absolute volume), Lufthansa (highest SAF share as a percentage of total fuel among legacy carriers), British Airways, and SAS.

Fleet Age as a Proxy Metric

Average fleet age is a useful rough proxy for fuel efficiency: newer aircraft burn 15–25% less fuel per seat than their predecessors. Airlines with the youngest average fleets include IndiGo (~4 years), Wizz Air (~5 years), and Spirit Airlines (~6 years). Legacy carriers with older fleets — some operating 737 Classics or A330s averaging 15+ years — perform significantly worse on this metric.

Carbon Reporting Quality

Airlines disclosing verified Scope 1, 2, and 3 emissions through CDP include Lufthansa, Air France-KLM, IAG, United, Delta, and Qantas. Airlines with CDP A or A- ratings demonstrate the most rigorous reporting. Non-disclosure or self-reported-only emissions data is a red flag for investors and sustainability analysts alike.

How to Choose a Greener Airline

For individual passengers: use Atmosfair's airline ranking before booking to identify the most fuel-efficient operator on your route. Prefer non-stop flights — connections multiply fuel burn. Choose economy class — business class carries 2–4× the carbon footprint per passenger. On routes where multiple airlines operate the same origin-destination pair, the aircraft type matters as much as the airline brand: a new A321neo versus an older 737-800 on the same route is a meaningful difference.