Sustainability targets are tightening and the pressure to cut carbon emissions is no longer a distant concern for the aviation industry, it is a requirement. At the heart of this shift is the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). It is a global framework designed to curb emissions from certain international flights and steer aviation towards net zero by 2050. So, what is CORSIA, how does it work, and what does it mean for your business?

Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) logo.

How does CORSIA work?

CORSIA was adopted in 2016 by the International Civil Aviation Organisation (ICAO), a UN agency responsible for making sure aircraft operators act in an environmentally responsible way. The scheme includes all aircraft operators, from passenger airlines, cargo airlines, business aviation, and private aviation. Aviation currently accounts for 2.5% of global CO₂ emissions, a figure that without intervention is set to rise as passenger demand continues to grow year on year.

Under CORSIA, operators of eligible international flights must monitor and report their annual carbon emissions.Under CORSIA, operators of eligible international flights must monitor and report their annual carbon emissions. Any increase above a 2019 baseline must be offset by buying eligible carbon credits, known as CORSIA Eligible Emissions Units (CEEUs). These obligations may be reduced through the use of  Sustainable Aviation Fuel (SAF), a renewable alternative to traditional jet fuel that lowers an airline’s overall carbon impact. The carbon credits purchased under the scheme are directed towards the investment in approved environmental projects, ranging from reforestation initiatives to renewable energy programmes. CORSIA therefore incentivises airline operators to reinvest into the environment, directly counterbalancing the impact of emissions they produce.

Which routes apply?

CORSIA  currently only applies to international flights that depart from and arrive in participating countries. Domestic aviation is not covered, a notable gap for large countries like the United States, where domestic travel makes up a substantial share of aviation emissions. Flights to or from non-participating states also fall outside the first phase. This matters given that some of the largest emitters, including China, Russia, and India, remain outside the scheme.

The first and second phrase of CORSIA

While global emissions have remained below CORSIA’s baseline levels, this is only the first phrase, which runs from January 1, 2024, to December 31st, 2026. During this period , participation remains voluntary, with the scheme applying only to flights between participating countries. As of 2026, 130 out of 193 member states are  participating in the programme, including the United Kingdom, covering approximately 60% of total international aviation emissions.

During the second phase, which runs from January 1st, 2027, to December 31st, 2035, participation becomes mandatory for all ICAO member states. With coverage expected to rise to around 85% of total international aviation emissions. It is worth noting that certain exemptions apply. Small islands, least developed countries, and land-locked countries which have less than 0.5% of air traffic are exempt from mandatory participation, though they may choose to join voluntarily. Aircraft with a Maximum Take Off Mass (MTOM) of 5,700kg or less, as well as humanitarian, medical, and state aircraft, also fall outside the scope of the scheme.

How to comply with CORSIA

Any aircraft operator with annual emissions greater than 10,000 tons of CO2  is required to monitor, report, and verify emissions data for each scheme year. Accurate reporting and transparency are essential, as failure to meet compliance obligations can result in civil penalties. As part of the compliance process, operators must develop an emission monitoring plan outlining key information about the operator, its fleet, and flight operations. The plan details the methods used to monitor fuel consumption, calculate emissions, and manage the associated data. Independent third-party verification then reviews this data and evaluates internal procedures to confirm that reporting standards have been met. Once data has been verified and submitted, the government works alongside ICAO to determine each operator’s offsetting obligations and inform operators of the number of eligible carbon credits required.

Operators are then required to purchase or surrender CEEUs accordingly, with each unit representing one tonne of CO2 equivalent reduced or removed through an approved environmental project. To ensure genuine environmental impact, these projects must deliver emissions reduction beyond what would have occurred under normal business activities. Operators can purchase these units through a broker, who acts as an intermediary within the carbon market, helping business source credits that meet compliance requirements.

How Purely Energy can help

Navigating CORSIA can be confusing and complex for aircraft operators, and the consequences of getting it wrong can be damaging. This is where Purely Energy comes in. Purely offers a dedicated Carbon compliance service designed to take the complexity out of carbon accounting, so operators can focus on what they do best.

Purely is developing its trading infrastructure, around UK Allowances (UKAs) under the UK Emissions Trading Scheme, and in the future CORSIA-eligible carbon credits such as Verra. Verra is one of the ICAO's approved programmes under CORSIA, meaning eligible Verra credits can be used by aircraft operators to meet their international aviation obligations. Understanding the difference matters: UKAs are compliance allowances under the UK ETS, covering domestic flights and departures to the EEA.

CORSIA, by contrast, uses credits from ICAO-approved programmes for international aviation. Whether operators are just getting to grips with their obligations or want to manage their carbon costs, Purely has the knowledge and tools to help them stay ahead. Helping them deliver operations smoothly rather than being weighed down by complexity of regulations.

If you have any queries about CORSIA or would like to lower your energy costs, contact us on 0161 521 3400 or email us at info@purelyenergy.co.uk .