ENVIRONMENTAL COMPLIANCE · By Ferhan Bugay, Executive Director, Aero Support Group FZCO · 4 November 2026
What is CORSIA?
CORSIA, the Carbon Offsetting and Reduction Scheme for International Aviation, is ICAO’s market-based measure for international flights. Airlines monitor and report their CO2 emissions every year and offset the growth in emissions above a baseline by cancelling eligible emissions units. Using CORSIA eligible fuels, including certified sustainable aviation fuel, reduces the offsetting requirement.
The requirements sit in Annex 16 Volume IV and are applied through each State’s national rules. Monitoring, reporting and verification has applied since 1 January 2019 to operators emitting more than 10,000 tonnes of CO2 a year on international flights.
What changes on 1 January 2027?
- Phases: the first phase covered 2024 to 2026. The second phase runs from 2027 to 2035, and participation is no longer voluntary for most States.
- Who is covered: States whose share of 2018 international revenue tonne-kilometres is at least 0.5%, or which are together within the top 90%, take part on a mandatory basis. Least developed countries, landlocked developing countries and small island developing States are exempt unless they volunteer.
- Volunteers: 130 States took part in 2026, and ICAO expects around 134 in 2027.
- Baseline: since 2024 the baseline has been 85% of 2019 CO2 emissions.
- Offsetting formula: until 2032 an operator’s requirement is calculated with the sector’s growth factor. For 2033 to 2035 the split moves to 85% sectoral and 15% individual, so an airline’s own growth starts to count.
Annex 16 Volume IV, third edition
The ICAO Council adopted Amendment 2 to Annex 16 Volume IV at its 237th session in March and April 2026. The resulting third edition is expected to apply from 1 January 2027, so the second phase starts with an updated rulebook. Operators should read the amended provisions against their Emissions Monitoring Plan and confirm with their State authority how the changes are being transposed into national rules.
Eligible emissions units are approved per compliance period. Ten programmes were approved for the first phase, and decisions on applications for 2027 to 2029 were scheduled for the 239th Council session in late 2026. Check the current ICAO list before buying units.
The annual cycle airlines must follow
- Monitor fuel use and CO2 emissions on international flights under the approved Emissions Monitoring Plan, using a fuel-use method or the ICAO CORSIA CO2 Estimation and Reporting Tool where eligible.
- Verify and report: submit the verified Emissions Report and the verification report to the State by 30 April each year.
- State reporting: States report to ICAO’s central registry by 31 July.
- Offsetting requirement: States notify operators of their offsetting requirements by 30 November.
- Cancel units equal to the final requirement for each three-year compliance period, net of any claims for CORSIA eligible fuels.
How CORSIA fits with the EU ETS and ReFuelEU
For flights to and from Europe, CORSIA is one of several overlapping schemes. The EU applies CORSIA to flights leaving the European Economic Area, while flights within the EEA fall under the EU ETS. On 17 July 2026 the European Commission proposed extending the EU ETS from 2029 to departures to non-EEA airports within 5,000 km of Frankfurt, with the cost of CORSIA deducted to avoid double charging. That proposal is still going through the legislative process.
SAF uplifted under ReFuelEU Aviation or the UK SAF Mandate can also count as a CORSIA eligible fuel if it is certified by an approved scheme and the claim is not double counted. Holding one fuel and emissions record that serves all schemes saves a lot of reconciliation work. More on this on our SAF and CORSIA compliance page.
What airlines should do before January
- Confirm whether your State and the States on your routes participate in 2027.
- Review the Emissions Monitoring Plan for fleet, network and method changes, and resubmit it if needed.
- Check that fuel data for CORSIA, the EU ETS and ReFuelEU come from one controlled source.
- Estimate offsetting exposure for 2027 to 2029 and decide how and when to buy eligible units.
- Document SAF purchases with sustainability certificates so that claims under CORSIA and other schemes hold up at verification.
Conclusion
The second phase turns CORSIA from a scheme many airlines watched into one most will have to comply with. The airlines that cope best will have a current monitoring plan, a single source of fuel and emissions data and a clear view of their offsetting costs before the first invoices arrive. ASG helps airlines get there.
Frequently asked questions
On 1 January 2027. It runs until 31 December 2035.
For most States, yes. States above the traffic thresholds in ICAO’s Assembly resolution participate on a mandatory basis. Least developed countries, landlocked developing countries and small island developing States are exempt unless they volunteer.
From 2024 the baseline is 85% of 2019 CO2 emissions from international aviation.
The ICAO Annex that sets the CORSIA standards and recommended practices. Its third edition is expected to apply from 1 January 2027.
Yes. CORSIA eligible fuels certified by an approved sustainability certification scheme reduce the offsetting requirement, provided the same fuel is not claimed twice.
Key takeaways
- CORSIA second phase runs from 1 January 2027 to 2035
- Participation becomes mandatory for most large aviation States
- Baseline is 85% of 2019 CO2 emissions
- Annex 16 Volume IV third edition expected from 1 January 2027
- Emissions reports are due to the State by 30 April each year
Getting ready for CORSIA in 2027?
Tell us your network and fleet. ASG will check your coverage, monitoring plan and offsetting exposure for the second phase.