What Is CORSIA? Definition, Purpose and Legal Basis

CORSIA — the Carbon Offsetting and Reduction Scheme for International Aviation — is a global measure adopted by the International Civil Aviation Organization that requires aircraft operators to offset the growth in carbon dioxide emissions from international flights above an agreed baseline.

It is the first market-based climate measure applied worldwide to a single industry sector.

The One-Sentence Definition

CORSIA requires operators of international flights to buy and cancel carbon credits equal to the amount by which the sector's emissions exceed its 2019 level, so that growth in international aviation is carbon neutral even though the flights themselves still emit.

Two words in that sentence do heavy lifting.

Growth. CORSIA does not ask operators to offset all their emissions. It asks them to offset the increase above a baseline. An operator flying exactly its 2019 volumes, in a sector that has not grown, owes nothing.

Offset. The emissions still happen. What the operator buys is a reduction achieved somewhere else in the world economy, which would not have happened without the payment.

What CORSIA Is Not

Being precise here prevents a lot of confusion.

That last row is the one most often misunderstood. State participation was voluntary in the pilot and first phases and becomes mandatory for most States in the second phase. Operator compliance, once a State participates, has never been voluntary.

Where the Legal Force Comes From

ICAO is a United Nations specialised agency. It cannot fine an airline directly.

The chain works like this:

1. The ICAO Assembly agrees the scheme by resolution.
2. The standards are placed in Annex 16, Volume IV to the Chicago Convention on International Civil Aviation.
3. Member States implement those standards in national law.
4. The national authority — the DGCA in India, the FAA in the United States, national competent authorities across Europe — approves monitoring plans, receives reports and enforces.

So the penalty for non-compliance is a matter of domestic law and varies by State. The obligation itself is uniform; the consequence of ignoring it is not.

The Three Things an Operator Actually Has to Do

1. Monitor and report emissions — every year, regardless of offsets

Every operator producing more than 10,000 tonnes of CO2 a year from international flights must have an approved Emissions Monitoring Plan, track fuel use by an approved method, submit an Annual Emissions Report, and have that report verified by an accredited independent body.

This applies whether or not any offsetting obligation arises. An operator flying only to non-participating States still monitors and reports.

See CORSIA MRV explained.

2. Calculate the offsetting requirement

Once ICAO publishes the growth factors for a year, the operator applies them to its verified emissions on covered routes and subtracts any reduction claimed for CORSIA Eligible Fuels.

The result is a number of tonnes to offset for that year, accumulating across the three-year compliance period.

See the requirement calculation.

3. Buy, cancel and report eligible units

The operator acquires CORSIA Eligible Emissions Units, cancels them in a registry with CORSIA designated as the purpose, and files an Emissions Unit Cancellation Report with the national authority.

Cancellation, not purchase, is what discharges the obligation. Holding units achieves nothing.

See registries and cancellation.

Why Not Any Carbon Credit?

This is the single most consequential fact about the scheme, and it surprises almost everyone new to it.

A carbon credit and a CORSIA credit are not the same thing. A unit must come from a crediting programme the ICAO Council has approved, fall within an eligible vintage window, and — the binding constraint — carry a corresponding adjustment from the government of the country where the reduction happened.

That last requirement means the host government must add the tonnes back into its own national emissions accounting, giving up the reduction against its own Paris Agreement target. Many governments decline. Many others have no process for doing it at all.

The result is that most of the world's carbon credits, including a great deal of genuinely high-quality supply, cannot be used for CORSIA. Eligible supply is a small, scarce and expensive subset.

See corresponding adjustments and Article 6.

Key Facts Table

Common Misconceptions

"CORSIA makes flying carbon neutral"

No. It aims at carbon neutral growth from a 2019 baseline, not carbon neutral flying. Emissions at or below the baseline are not addressed by the scheme at all, and the emissions above it still physically occur — they are compensated by reductions elsewhere.

"My airline is small, so CORSIA does not apply"

Check the threshold before assuming. It is 10,000 tonnes of CO2 a year from international flights, which is a smaller operation than most people expect. And even below the offsetting threshold, reporting obligations may still apply depending on your State's implementation.

"We already buy carbon credits, so we are covered"

Almost certainly not. Voluntary market credits rarely satisfy the CORSIA eligibility criteria, chiefly because they lack a host-State corresponding adjustment. Buying credits and buying CORSIA-eligible units are different procurement exercises in different markets at different prices.

"CORSIA replaces the EU ETS"

It does not. An operator flying within Europe can face both. The two schemes use different instruments — allowances against credits — and their scopes have been arranged to limit duplicate obligation on the same emissions. See CORSIA vs EU ETS and other schemes.

"Sustainable aviation fuel exempts us"

SAF reduces the obligation rather than removing it, and only when the fuel meets the CORSIA Eligible Fuels sustainability criteria, is certified under an approved scheme, and the chain of custody is documented. Burning qualifying fuel without the paperwork produces an environmental benefit and no CORSIA claim.

Where to Go Next

• Why CORSIA exists — the history that shaped the design
• How CORSIA works — the mechanism end to end
• CORSIA scope and thresholds — whether you are in
• CORSIA phases and timeline — what changes and when
• CORSIA glossary — every term defined

The authoritative source is ICAO's CORSIA pages. Treat any secondary summary, this one included, as an orientation rather than a compliance reference.

Getting Help

DSTechnoverse provides specialist CORSIA carbon credit services for aircraft operators and project developers, from Indore, Madhya Pradesh and across India. If you are working out whether CORSIA applies to you, or what it will cost, talk to our carbon markets team.

Apply as a CORSIA buyer or seller