Explained: The ICAO CORSIA Scheme

We take a closer look at the ICAO CORSIA Scheme initiative, which aims to reduce the industry's carbon footprint in the next decades.



February 23, 2023

DALLAS — The International Civil Aviation Organization's (ICAO) Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) is a global market-based measure (MBM) to reduce greenhouse gas (GHG) emissions produced by commercial aviation.

CORSIA was adopted at the 39th Assembly of ICAO in 2016. The scheme is the first global initiative implemented by ICAO to address climate change. Its background, objectives, mechanisms, issues, steps, and possibilities are discussed in this post.

By Alinor at en.wikipedia - Own work (Original text: I (Alinor (talk)) created this work entirely by myself.),
ICAO headquarters. Photo: Alinor at en. Wikipedia - Own work CC BY-SA 4.0


Aviation accounts for 2.4% of global CO2 emissions. Though it is a small number compared to other forms of land transportation, according to the International Energy Agency (IEA), the number of air passengers is expected to double by 2040, and the demand for air transport is projected to increase by 3.7% per year.

In response to this challenge, ICAO developed a global MBM called CORSIA, which aims to achieve carbon-neutral growth from 2020 onward and reduce the aviation sector's carbon footprint.

CORSIA is part of ICAO's basket of measures, which includes technology development, operational improvements, and alternative fuels.

By ICAO - Corsia Brochure, Public Domain,
By ICAO - Corsia Brochure, Public Domain, https://commons.wikimedia.org/w/index.php?curid=97207882


The primary objective of CORSIA is to limit the growth of net aviation CO2 emissions to 2020 levels. The scheme is voluntary in the first phase (2021-2023) and mandatory for most states in the second phase (2024-2035). The goal of CORSIA is to achieve a collective emission reduction of 2.6 billion tonnes of CO2 by 2040.

The specific objectives of CORSIA are:

  1. To achieve carbon-neutral growth in international aviation from 2020 onwards: It aims to stabilize the net carbon emissions of international aviation at 2020 levels by offsetting any emissions that exceed these levels.
  2. To reduce the carbon footprint of the aviation sector: CORSIA aims to reduce the carbon footprint of the aviation sector by promoting the use of more fuel-efficient aircraft, sustainable aviation fuels, and low-carbon technologies.
  3. To encourage global cooperation and collaboration: The scheme aims to encourage global cooperation and collaboration by establishing a common framework for carbon offsetting and reducing emissions from international aviation.
  4. To promote sustainable development: The initiative aims to promote sustainable development by providing financial incentives for the development of sustainable aviation fuels and low-carbon technologies, as well as by contributing to the achievement of the United Nations Sustainable Development Goals.
  5. To support the Paris Agreement on climate change: CORSIA aims to support the Paris Agreement on climate change by contributing to the reduction of global greenhouse gas emissions, in line with the goal of limiting global temperature increase to well below 2 degrees Celsius.

By achieving these objectives, CORSIA aims to contribute to the global effort to mitigate climate change, while also promoting the sustainable development of the aviation sector.

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ICAO CORSIA Scheme | Photo: ICAO


CORSIA works on a carbon offsetting basis, where airlines are required to offset their emissions by purchasing emission reduction units (ERUs) from eligible projects.

ERUs are credits that represent a reduction of GHG emissions by a project that is certified by an approved international standard. ERUs can be purchased from various sources, such as renewable energy projects, forest conservation, and energy efficiency.

The CORSIA system consists of three stages: the Pilot Phase (2019-2020), the First Phase (2021-2023), and the Second Phase (2024-2035). The chart created by aviationbenefits.org clearly shows the expected implementation of the scheme in phases starting from 2019 to 2035.

ICAO CORSIA Scheme | Photo: By aviationbenefits.org

In the Pilot Phase, ICAO tested the feasibility of the scheme, and several states and airlines participated voluntarily.

In the First Phase, which started in 2021, the scheme will be voluntary for most states, and only states with significant international aviation activities will be required to participate.

In the Second Phase, which starts in 2024, most states will be required to participate in the scheme.

N57004 Boeing Company (Blue Air) Boeing 737-8 MAX Unpainted KPDX PDX
N57004 Boeing Company (Blue Air) Boeing 737-8 MAX Unpainted KPDX PDX | Photo: Brandon Farris/Airways


CORSIA faces several challenges, including the following:

  1. Monitoring, Reporting, and Verification (MRV): The success of CORSIA depends on the accuracy and reliability of MRV of airlines' emissions and ERUs. ICAO has developed a set of guidelines and requirements for MRV, but there are still challenges in harmonizing the different MRV systems and ensuring transparency and consistency.
  2. Eligibility of ERUs: The quality and reliability of ERUs are essential for the integrity of the scheme. ICAO has established a list of eligible standards and criteria for ERUs, but there are concerns about the additionality and permanence of some projects.
  3. Equity and fairness: CORSIA aims to achieve a collective emission reduction, but the distribution of the burden among states and airlines may not be equitable or fair. There are concerns about the impact of CORSIA on developing countries and small island states that heavily rely on tourism.
  4. Double counting: There is a risk of double counting emission reductions, where the same reduction is claimed by both the buyer and the seller of the ERU. ICAO has established a set of rules and procedures to avoid double counting, but there are still concerns about the effectiveness of these measures.
  5. Transparency and governance: The success of CORSIA also depends on the transparency and governance of the scheme. ICAO has established a governance structure, including a Technical Advisory Body (TAB) and an Emissions Unit Criteria Body (EUCB), but there are concerns about the independence and effectiveness of these bodies.
CORSIA member and nonmember States | Photo: IATA CORSIA Factsheet


Despite the challenges, CORSIA also presents several opportunities and they are as follows:

  1. Climate change mitigation: CORSIA has the potential to reduce the aviation sector's carbon footprint and contribute to the global effort to mitigate climate change. The scheme is expected to achieve a collective emission reduction of 2.6 billion tonnes of CO2 by 2040.
  2. Innovation and investment: CORSIA could also stimulate innovation and investment in low-carbon technologies and alternative fuels, such as electric and hybrid planes, sustainable aviation fuels (SAF), and hydrogen-powered planes.
  3. Collaboration and cooperation: CORSIA provides an opportunity for international collaboration and cooperation to address the global challenge of climate change. The scheme involves the participation of states, airlines, and carbon market stakeholders from around the world.
  4. Sustainable development: CORSIA could also contribute to sustainable development by promoting renewable energy, forest conservation, and energy efficiency projects. These projects could generate co-benefits, such as job creation, biodiversity conservation, and poverty reduction.
Boeing N772ET Boeing 777-200(ecoDemonstrator Livery)
Boeing N772ET Boeing 777-200(ecoDemonstrator Livery) | Photo: Brad Tisdel/Airways


While CORSIA is a significant milestone in the global effort to mitigate climate change, it is only a starting point. As stated earlier, the aviation sector is responsible for around 2.5% of global greenhouse gas emissions, and this is expected to grow as air travel continues to expand. Therefore, there is a need to develop additional measures to reduce the aviation sector's carbon footprint.

One such measure is the development and promotion of sustainable aviation fuels (SAF). SAFs are fuels that are derived from renewable resources, such as biomass, waste, and non-food crops. They have the potential to reduce emissions from the aviation sector by up to 80% compared to conventional jet fuel.

Photo: Sustainable Aviation Fuel Guide title by ICAO

However, SAFs currently account for less than 1% of the aviation fuel market, and their production is still limited by high costs and technical challenges. Therefore, there is a need to invest in research and development, and to establish policies and incentives to promote their use.

Another measure is the promotion of energy efficiency and the use of low-carbon technologies. The aviation sector has already made significant progress in this area, such as with the development of more fuel-efficient planes and the implementation of operational measures to reduce emissions, such as optimized routes and descent procedures.

There is still room for improvement, and more needs to be done to accelerate the deployment of low-carbon technologies.

N171US American A321 SAN KSAN (Airlines Combo)
N171US American A321 SAN KSAN (Airlines Combo) | Photo: Jinyuan Liu/Airways


The success of CORSIA depends on the participation of all states and airlines. Only a small number of states have committed to participating in the scheme. Also, major airlines have expressed reservations about its effectiveness and feasibility.

Consequently, ICAO notes that it is necessary to interact with all stakeholders and address their concerns to guarantee the greatest possible involvement in the program.

N787FT Boeing Company Boeing 787-8 Dreamliner KPAE PAE
N787FT Boeing Company Boeing 787-8 Dreamliner KPAE PAE | Photo: Brandon Farris


CORSIA is a big step forward in the industry's worldwide attempt to reduce the impact of climate change and lower the aviation sector's carbon footprint. This program offers various opportunities, such as climate change mitigation, creativity and investment, teamwork and collaboration, and sustainable growth.

Airlines can now hire CORSIA Executive staff members to monitor their carbon emissions and provide data such as fuel burn rates to regulatory authorities. ICAO and IATA are able to provide certifications for the CORSIA scheme.

CORSIA faces a number of obstacles, such as monitoring, reporting, and verification; whether or not ERUs qualify; fairness and equity; double-counting; and transparency and governance. These issues need to be addressed with effective regulations, guidelines, and governance in order to guarantee the scheme's reliability and efficacy.

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Feature Image: Cathay Pacific Airbus A350 | Photo: Noah Pitkin/Airways