CorsiaEdit
Corsia is an international effort to curb emissions from international aviation through a global market-based mechanism. Formally known as the Carbon Offsetting and Reduction Scheme for International Aviation, the program is coordinated by ICAO and is designed to keep the growth of aviation emissions in check by requiring airlines to offset the increase in CO2 beyond a pre-set baseline. The overarching idea is to avoid a patchwork of unilateral regulations while nudging the industry toward lower emissions through offset purchases and, over time, greater efficiency and the adoption of Sustainable aviation fuel and other cleaner technologies.
In keeping with a practical, market-friendly approach, Corsia seeks to align aviation policy with broader climate objectives without imposing a heavy-handed regulatory regime. The framework is built around verifiable emissions reductions secured through internationally recognized offset projects, with reporting and verification standards designed to minimize fraud and double counting. The scheme also interacts with national and supranational climate policies, including Paris Agreement, by providing a uniform mechanism that complements country-level efforts rather than replacing them.
History
Corsia was developed in response to the fragmented patchwork of national and regional policies affecting international aviation. In 2016, at the ICAO Assembly, member states agreed to launch a global market-based measure to address aviation emissions in a way that would be globally applicable and less prone to competitive distortions than a series of disparate national rules. The agreement established a baseline year of 2020 and a mechanism for airlines to offset growth in emissions above that baseline.
Implementation is structured in phases. The early period, often described as a pilot phase, ran roughly from 2021 to 2023 to test monitoring, reporting, verification (MRV) procedures and the reliability of emissions reductions from eligible offset projects. The subsequent phase, commonly referred to as the first phase, began in the mid-2020s and gradually expanded the scope of compliance. A second, longer-term phase was planned to bring universal participation and tighter requirements as the system matures. Throughout its history, Corsia has been shaped by feedback from industry, regulators, and climate advocates who weighed the balance between environmental ambition and the needs of a globally connected aviation sector.
The program has also interacted with broader debates about how to price carbon, how to compare offset quality, and how to ensure that aviation remains competitive for travelers and for businesses that rely on international air travel. As with other global schemes, the exact pace of expansion and the stringency of offset criteria have been subject to political and economic considerations.
How it works
Corsia rests on a few core pillars. First is the baseline, which uses 2020 aviation emissions as the reference point. Growth in emissions above that baseline must be offset by purchasing credits from eligible emissions-reduction projects. Second is the offset mechanism: airlines acquire offsetting credits that represent verified emission reductions, typically from projects in other sectors and regions. The credits are intended to be real, additional, verifiable, permanent, and enforceable, meeting internationally recognized standards for emissions reductions.
Key procedural elements include Monitoring, Reporting and Verification—the process by which airlines measure and report their international flight emissions—and the governance of emissions trading offsets through CEUs (CORSIA Eligible Emissions Units), which must meet established criteria to be considered valid for compliance. In practice, airlines purchase offsets to cover emissions growth above the 2020 baseline, thereby achieving net-zero growth for international aviation on aggregate, even as absolute emissions may continue to rise in the short term due to overall travel demand.
Corsia also encourages the use of cleaner technology and fuels. Airlines and governments alike are incentivized to accelerate the deployment of Sustainable aviation fuel and invest in more efficient aircraft, improved flight operations, and other innovations that can deliver real emissions reductions in addition to the offset program. The interaction with SAF is a central piece of the long-term strategy, because offsets alone cannot sustain limitless growth if technological progress remains slow.
The program has a global scope, covering international routes between participating states. While participation is voluntary for individual states, the mechanism is designed so that widespread participation minimizes competitive distortions and creates a level playing field for carriers operating across borders. The scheme also dovetails with broader climate objectives Paris Agreement by contributing to the decarbonization of one of the world’s most transportation-intensive industries.
Coverage and participation
A large share of international aviation traffic is covered by Corsia through participating states and carriers. States opt into the program, and airlines operating international routes registered with those states are subject to offset requirements. The framework maintains transparency by requiring public reporting of emissions data, offset purchases, and project details so stakeholders can assess progress and reliability. The design aims to avoid double counting by ensuring that offsets are retired when used for Corsia compliance, a mechanism that is essential to maintaining environmental integrity across the system.
Critically, Corsia is not a universal ban or tax on flying. Rather, it is a strategic, market-based instrument that seeks to internalize the environmental costs of growth in international aviation. It is compatible with a broad range of national and regional policies and is intended to reduce the risk that countries adopt duplicative or punitive measures that could hinder global commerce or raise travel costs for consumers.
Economic and policy implications
From a policy standpoint, Corsia represents a pragmatic balance between environmental goals and the realities of a highly interconnected global economy. By creating a predictable, global framework, it helps stabilize the cost environment for airlines and encourages long-run investments in efficiency and SAF. The approach reduces the incentive for individual jurisdictions to impose their own, potentially conflicting, carbon policies on international aviation, which can create compliance complexity and added costs for carriers.
Proponents argue that Corsia yields several benefits: it lowers the marginal cost of reducing emissions compared with a patchwork of regulations; it channels finance toward credible emissions-reduction projects; and it speeds the adoption of cleaner aviation technologies by tying regulatory compliance to market mechanisms and innovation incentives. Critics, however, worry about the quality and price of offsets, the potential for offsets to deliver less-than-full additionality, and the risk that the program could become a bureaucratic overlay that fails to deliver commensurate environmental improvements if demand for offsets remains weak or if credit quality is inconsistent.
Supporters contend that offset credits are subject to rigorous standards and verification regimes, with ongoing improvements to ensure that projects deliver verifiable emissions reductions. They also point out that Corsia complements, rather than substitutes for, national climate action and can serve as a bridge to more ambitious decarbonization strategies as technology and fuels become more affordable and scalable.
Controversies and debates
Like many global climate initiatives, Corsia has sparked debates about effectiveness, equity, and the best path to decarbonization. Supporters emphasize that it provides a cost-effective way to curb emissions growth in a sector where immediate, absolute reductions are technically challenging and economically disruptive if pursued through regulation alone. They argue that the program fosters investment in more efficient aircraft, air traffic optimization, and the scaling of SAF, which can deliver measurable benefits beyond offsets.
Opponents raise several concerns. Some argue that offsets do not always correspond to real, additional, or permanent emissions reductions, particularly when projects could have occurred without Corsia’s involvement or when credit quality is inconsistent. Critics also worry about price volatility and the risk that offsets become a loophole for airlines to avoid investing in technology or operations improvements. There are further concerns about sovereignty and the risk that a globally standardized policy might not reflect domestic priorities or particular economic conditions.
From a broader political perspective, some critics frame Corsia as a step toward global governance of aviation that could undermine national discretion over environmental and trade policy. Proponents respond that the framework preserves national sovereignty by letting states participate on voluntary terms while avoiding a patchwork of unilateral rules. They emphasize that the program is designed to be fiscally neutral for governments, with offset purchases serving as a mechanism to finance emissions reductions without direct taxation or new government programs.
Woke criticisms of Corsia—typical in broader climate debates—argue that offset schemes may allow industries to delay meaningful cuts and that the global nature of the policy can obscure local tradeoffs and economic burdens. A right-leaning perspective frequently counters that well-structured offsets actually channel private sector capital into verifiable reductions, create market incentives for efficiency and SAF adoption, and avoid the distortions associated with heavy-handed regulations or sector-specific taxation. The rebuttal emphasizes that Corsia’s design includes verification, transparency, and international oversight, and that it is a practical, incremental step toward cleaner aviation without sacrificing global mobility or economic growth.