8 mins read
Published Jan 26, 2026
Understanding the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) Scheme
Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) is a global program developed by the International Civil Aviation Organization (ICAO) to curb the growth of carbon emissions from international air travel.
Agreed in 2016 and launched in 2019, CORSIA is the first worldwide market-based climate scheme for any single industry sector. It requires airlines to monitor and report their CO₂ emissions on international routes and offset any increase above a set baseline level by funding equivalent carbon reductions (offsets) elsewhere or by using cleaner fuels.
How CORSIA Works and Its Goals
The baseline was originally going to be the average of 2019–2020 emissions, but due to the COVID-19 traffic collapse in 2020, ICAO adjusted it. For the pilot phase (2021–2023), 2019 emission levels alone were used as the baseline.
More recently, ICAO made the baseline even more stringent: from 2024 onward, airlines must offset growth beyond 85% of their 2019 emissions. This means the industry’s net CO₂ output should stay roughly 15% below 2019 levels in the coming years, a more ambitious target than originally planned.
Offsetting requirements under CORSIA began in 2021, with airlines required to demonstrate compliance at the end of each multi-year period by cancelling the appropriate number of carbon credits (emissions units) that equal their excess emissions. By keeping net emissions at or below the baseline, it is forecasted that CORSIA would stabilise international aviation CO₂ emissions at about 550–600 million tonnes per year from 2024, and avoiding over 1 billion tonnes of CO₂ by 2035.
It’s important to note that CORSIA applies only to international flights (flights between different countries) and that domestic aviation emissions are not covered at this stage.
Phased Implementation and Global Participation
Phase | Years | Participation Type | Key Features | Coverage & Notes |
Pilot Phase | 2021–2023 | Voluntary |
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First Phase | 2024–2026 | Voluntary |
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Second Phase | 2027–2035 | Mandatory (with exemptions) |
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*States classified as Least Developed Countries (LDCs), Small Island Developing States (SIDS), or Landlocked Developing Countries (LLDCs) as well as states with very low aviation activity, are exempt by default, unless they volunteer to opt in. (Many have voluntarily joined regardless, as a sign of climate leadership.)
Source: IATA (2024), Adapted by NoviqTech (2026)
Monitoring, Reporting, and Verification (MRV) of Emissions
CORSIA’s MRV framework ensures consistent, transparent emissions data across operators.
Emissions Monitoring
Operators must monitor fuel consumption for each international flight and calculate CO₂ emissions under an approved Emissions Monitoring Plan according to the framework.
Annual Reporting
Every year, operators submit an Emissions Report to their State authority. Reports are verified by an accredited independent body (ISO 14065) and then consolidated by the State for upload to ICAO’s Central Registry.
Verification
Only independent verification bodies accredited by a national accreditation body and recognised by the administering State may verify reports, covering methods, fuel use records, flight data and cancellation of emissions units under Appendix 6 of Annex 16, Vol IV.
Small-Emitter Provisions
Operators whose international-flight CO₂ emissions are ≤ 10 000 tonnes (for aircraft with > 5 700 kg) are exempt from reporting. Operators < 50 000 tonnes may use ICAO’s CERT tool; those ≥ 50 000 tonnes must use a full Fuel Use Monitoring Method.
Data Flow and Offsetting
After verification, States relay data to ICAO. ICAO calculates sectoral and individual growth factors and informs operators of offsetting obligations. Airlines must cancel eligible emissions units at the end of each compliance period (e.g., 2024-2026, 2027-2029), in line with Annex 16, Vol IV Chapter 3.
Example (illustrative): Suppose Airline A emitted 120,000 tonnes of CO₂ on covered international flights in 2024. If its 2019 baseline emissions were 100,000 tonnes, the growth is 20,000 tonnes. However, ICAO may determine that in 2024 the sector-wide growth factor is, say, 80% (meaning 80% of that 20,000 must be offset by sectoral formula, the rest deferred to future individual obligation). If so, Airline A’s offset obligation for 2024 could be 16,000 tonnes of CO₂. The airline would plan to acquire 16,000 carbon credits or use equivalent fuel credits by the end of the compliance period. All these details are tracked through the MRV process to ensure transparency and accuracy.
CORSIA Eligible Fuels (CEF)
Under CORSIA, airlines can lower their offsetting obligations by using certified low-carbon fuels known as CORSIA Eligible Fuels (CEF):
Sustainable Aviation Fuel (SAF): Alternative jet fuels from renewable or waste-based sources that meet CORSIA sustainability and lifecycle requirements.
Lower Carbon Aviation Fuel: Certain non-renewable fuels that achieve a verified lifecycle CO₂ reduction relative to conventional jet fuel.
How it works
Each tonne of CO₂ avoided through eligible fuel use reduces an airline’s offsetting requirement on a one-to-one basis within the compliance period.
Eligibility criteria
Minimum lifecycle GHG reduction threshold: at least 10% versus conventional jet fuel, calculated across the full lifecycle, including indirect emissions from land-use change (ILUC) where applicable.
Certification by an ICAO-approved Sustainability Certification Scheme (SCS): for example, RSB and ISCC. Schemes audit sustainability, chain-of-custody traceability up to the blending point, and lifecycle GHG calculations.
Lifecycle accounting: ICAO default values may be used, or verified actual values if available and compliant with CORSIA methodology. The 10% threshold must be met after ILUC adjustments.
Example (illustrative): An airline burns 1,000 tonnes of a certified SAF made from municipal solid waste, which has 70% lower life-cycle emissions than fossil jet fuel. If burning 1,000 t of normal jet fuel would emit ~3,160 tCO₂, this SAF’s use avoids 2,212 tCO₂. The airline can subtract ~2,212 tonnes from its offsetting requirement for that year, directly reducing how many credits it needs to buy. This is how CEF usage translates into compliance benefits.
CORSIA has built-in flexibility on when to apply the fuel credits: ICAO recommends airlines claim the emissions reduction in the same year the fuel was used (to promptly reflect lower emissions. But airlines are allowed to claim the savings at any point within the compliance period in which the fuel was used. For instance, SAF used in 2025 could be claimed in the 2025 report, or the airline might wait and apply it in 2026, as long as it’s claimed by the end of that 2024–2026 phase.
This flexibility can help airlines manage year-to-year fluctuations.
CORSIA Eligible Emissions Units (CEEU): Carbon Offsets for Aviation
The other pillar of CORSIA compliance is the use of carbon offset credits, formally known as CORSIA Eligible Emissions Units (CEEUs). Each credit represents one tonne of verified CO₂ reduction or removal that airlines can purchase and retire to meet offsetting obligations.
Programme approval
ICAO’s Technical Advisory Body (TAB) evaluates carbon standards against its Emissions Unit Criteria (EUC). The ICAO Council then approves specific programmes whose credits meet those criteria.
As of 2025, six programmes are approved for use:
Gold Standard (GS)
Verra’s Verified Carbon Standard (VCS)
Climate Action Reserve (CAR)
Global Carbon Council (GCC)
American Carbon Registry (ACR)
Architecture for REDD+ Transactions (ART-TREES)
Core eligibility requirements
To qualify as a CORSIA-eligible unit, credits must:
Originate from an ICAO-approved programme that meets the Emissions Unit Criteria.
Represent real, measurable, additional, permanent and independently verified reductions.
Come from projects with a start date on or after 1 January 2016, ensuring post-Paris Agreement relevance.
Avoid double-counting or double-claiming through the use of corresponding adjustments under Article 6 of the Paris Agreement.
Undergo robust MRV processes and include safeguards for leakage, permanence and social and environmental integrity.
Implementation and tracking
Approved registries label qualifying credits as “CORSIA Eligible.” Once purchased, airlines must cancel (retire) these credits within the registry and report serial numbers to their national authority. The data are then recorded in ICAO’s Central Registry, which tracks compliance globally. ICAO periodically reviews the list of approved programmes to maintain market integrity.
Example (illustrative): An airline with a 50 000 t CO₂ offset obligation can retire 50 000 CORSIA-eligible credits, say, from a renewable-energy project under Gold Standard, to meet that requirement. Once cancelled for CORSIA, those units cannot be reused or claimed by any other entity.
Airlines will likely build portfolios of offsets balancing quality and cost. It’s expected many will favour cost-effective emissions units (often nature-based or renewable energy projects) to meet their obligations, especially if SAF remains relatively expensive. The market dynamic between buying offsets versus investing in pricier sustainable fuel will be influenced by relative prices.
Conclusion
CORSIA represents a landmark agreement in tackling aviation’s climate impact at a global level. It creates a framework where airlines take responsibility for growth in emissions by investing in emissions reductions, whether through market-based offsets or by adopting cleaner fuels. The scheme’s success hinges on effective implementation – from accurate monitoring of billions of tonnes of CO₂, to strict enforcement of quality criteria for offsets and fuels, to the willingness of states and airlines to participate and comply.
So far, most countries have joined, and the first compliance cycle is underway, heralding a new era of accountability for aviation emissions.
There are challenges ahead (ensuring sufficient supply of high-quality offsets and sustainable fuels and eventually transitioning from offsetting to actual emission cuts in line with net-zero 2050 goals). Yet, CORSIA provides an important near-term solution to curb aviation’s carbon footprint while longer-term technologies (like electric or hydrogen aircraft) are still in development. It also establishes a global carbon market mechanism for aviation, which can be built upon.
Crucially, implementation tools and expertise will play a big role in CORSIA’s effectiveness. By offering end-to-end fuel traceability, emissions tracking, and compliance management, Fuel Central is helping to ensure that the data and claims behind CORSIA are reliable.
Such leadership in sustainability tech not only aids airlines in meeting CORSIA obligations but also builds confidence among regulators and the public that aviation’s climate commitments are being transparently met.
In a global scheme as complex as CORSIA, trusted data and verification are everything, and with the right digital infrastructure, the industry can soar toward its emissions goals with clarity and credibility. Contact us today for a strategy call.
