Carbon Offsetting and Reduction Scheme for International Aviation

The Carbon Offsetting and Reduction Scheme for International Aviation is the first global market-based measure applied to any international industry sector, adopted by the International Civil Aviation Organization in 2016 to cap net CO2 emissions from international aviation at 2020 levels. CORSIA operates through a straightforward mechanism: airlines that grow their international CO2 emissions above a defined baseline must purchase and retire carbon offset credits equivalent to the excess emissions, channeling capital toward emission reduction projects in other sectors while the industry develops lower-carbon technologies and fuels.

What Is CORSIA?

CORSIA was conceived as a bridging measure. Aviation could not credibly promise immediate decarbonization given that aircraft entering service today will operate for 25 to 30 years, and that no zero-emission propulsion technology is ready for long-haul commercial operations. CORSIA acknowledges this reality while establishing a financial incentive for airlines to reduce fuel burn and adopt SAF as quickly as economics and supply allow. The scheme is administered by ICAO and applies to international routes between participating states — domestic flights are excluded and are instead subject to individual national policies such as the EU Emissions Trading System. Monitoring, reporting, and verification of emissions follows ICAO's MRV standards, which require airlines to submit annual emission reports verified by accredited third parties.

How It Works in Practice

Airlines operating international routes above a threshold of 10,000 tonnes of CO2 per year are subject to CORSIA. The scheme runs in phases: a voluntary pilot phase covered 2021 to 2023, a voluntary first phase covers 2024 to 2026, and a mandatory second phase from 2027 to 2035 will require participation from states responsible for roughly 90 percent of international aviation activity. Eligible offset units must be approved by ICAO's Technical Advisory Body and come from programs such as the Gold Standard, Verra's Verified Carbon Standard, and the American Carbon Registry. Airlines can also receive credit for SAF usage, reducing their offsetting obligation based on the lifecycle carbon savings of the fuel consumed.

Why It Matters

CORSIA is significant not because it directly reduces emissions — offsets do not eliminate the CO2 from combustion — but because it establishes international accountability and creates a financial cost for emission growth that did not previously exist. Airlines that increase efficiency and adopt SAF faster than competitors gain a competitive cost advantage, as their offsetting obligation is lower. Critics argue the scheme is insufficiently ambitious, noting that the 2020 baseline was set during a year when COVID-19 grounded most international aviation, potentially locking in an artificially low threshold. Proponents counter that CORSIA is the only framework capable of achieving global participation, including from major aviation states like China, the United States, and India, making it a necessary complement to regional mechanisms.

Key Facts and Figures

• CORSIA applies to approximately 13,000 international routes operated by airlines from over 100 participating states.
• The 2020 reference year baseline was set at 85 percent of the average of 2019 and 2021 actual emissions.
• Offset credits approved for CORSIA use span categories including forestry, renewable energy, methane capture, and industrial gas destruction.
• Aviation CO2 from international routes subject to CORSIA totaled approximately 400 million tonnes annually pre-COVID.
• Airlines can earn SAF credit under CORSIA for fuels certified with at least a 10 percent lifecycle carbon reduction.
• ICAO's 193 member states adopted CORSIA by consensus at the 39th Assembly in 2016.

Related Concepts

Carbon Offset, ETS Aviation, Net-Zero Aviation, Sustainable Aviation Fuel, Carbon Intensity