CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) is a program established by the International Civil Aviation Organization (ICAO) to limit and offset CO2 emissions from the international aviation sector. Its adoption is voluntary for all those who wish to participate. However, from 2027, the program will be mandatory for the majority of ICAO Member States, with some exceptions (developing countries, low-emission countries, etc.). This program aims to promote the stabilization of CO2 emissions from international aviation from 2020 onward, by encouraging the use of sustainable fuels and cleaner technologies to achieve carbon-neutral growth for aviation by 2035.
For further information see https://www.icao.int/CORSIA.