CORSIA Reporting for Wet Leases and Damp Leases
· DSTechnoverse · CORSIA & Carbon Markets
ACMI arrangements put one operator on the aircraft and another on the ticket. Which one reports, why the AOC settles it, and the data flow that has to exist between them.
A wet lease places an aircraft, crew, maintenance and insurance with one party while the commercial flight is sold by another. Passengers board a flight marketed by Airline A, operated by Airline B's aircraft and Airline B's crew, under Airline B's AOC.
For CORSIA, that last clause is the whole answer. But the arrangements in practice are more varied than the textbook definitions, and the data flow the arrangement requires is almost never set up in advance.
The three lease types, and what differs
| Dry lease | Damp lease | Wet lease (ACMI) | |
|---|---|---|---|
| Aircraft provided by | Lessor | Lessor | Lessor |
| Crew provided by | Lessee | Mixed — often cockpit from lessor | Lessor |
| Maintenance | Lessee | Lessor | Lessor |
| Insurance | Lessee | Usually lessor | Lessor |
| AOC used | Lessee | Depends on the arrangement | Lessor |
| CORSIA reporting | Lessee | Follows the AOC | Lessor, usually |
The damp lease row is deliberately hedged, because "damp lease" is a commercial description rather than a regulatory category. Arrangements described as damp leases vary considerably, and the CORSIA answer follows the AOC in each case rather than the label.
The practical test: whose AOC authorises the flight? That entity is the aeroplane operator. If the answer is unclear from the contract, it will be clear from the operations manual and the regulatory approval for the arrangement.
Why this matters commercially
Wet leases are frequently seasonal or short-term — additional capacity for a peak, cover for an aircraft in maintenance, or a route launch before an operator's own aircraft is available. The CORSIA consequences run in both directions and are rarely priced.
| Party | Effect |
|---|---|
| Lessor (operating carrier) | Emissions count towards its threshold and offsetting obligation |
| Lessee (marketing carrier) | No CORSIA obligation for those sectors |
| Lessor near the threshold | A season of wet lease flying may push it over |
| Lessee reducing its own flying | Its own emissions fall correspondingly |
An operator that wet-leases capacity out during a slow season is exporting emissions to the lessee's network while retaining them on its own CORSIA account. That is counter-intuitive commercially — the revenue is a lease fee rather than ticket sales, but the emissions and the offsetting cost stay with the operating carrier.
For an ACMI specialist whose entire business is wet leasing, this means the full emissions of every sector flown for every customer sit on one operator's obligation. It should be priced into the ACMI rate, and frequently is not.
The data flow that has to exist
Where the lessor reports, the lessor needs the data. That sounds obvious and breaks down in practice because the lessee often controls the ground arrangements.
| Data item | Frequently held by |
|---|---|
| Fuel uplift records | The lessee, who arranged the fuel contract |
| Handling agent dockets | The lessee's agent |
| Actual routing and block times | The lessor's own operations records |
| Aerodrome pairs flown | Both |
| Diversions and tech stops | The lessor's operations, the lessee's ground staff |
The first two are the problem. Under many ACMI arrangements the lessee arranges and pays for fuel, so the uplift records go to the lessee's account. The lessor, who must report the emissions, has no direct access.
The remedy is contractual and simple:
| Clause | Requirement |
|---|---|
| Fuel data provision | Lessee provides per-uplift records monthly, in a defined format |
| Timing | Within a stated number of days of month end |
| Format | Aircraft registration, date, station, quantity, units, density |
| Retention | Five years, with a right to request post-termination |
| Verification cooperation | Lessee provides records if the lessor's verifier requires them |
| Dispute mechanism | Where records are incomplete |
Without these, an ACMI operator reaches verification holding flight records for sectors whose fuel data belongs to a customer it may no longer be working with.
Short-term and ad-hoc arrangements
The compliance risk is concentrated in short arrangements, because nobody sets up a process for six weeks of flying.
Practical approach for a short wet lease:
- Confirm in writing, before the first flight, which party is the aeroplane operator.
- Agree the fuel data flow in the same document, however briefly.
- Have the lessor's own crew record fuel on board figures in the technical log as a backstop.
- Capture uplift dockets at the point of uplift — a photograph filed to a defined location is sufficient.
- Reconcile at the end of the arrangement, not at year end.
Point three is the practical safety net. Where the contractual data flow fails, technical log figures recorded by the lessor's own crew provide corroborating evidence that can support a reconstruction — see missing fuel uplift records.
Sub-charter chains
A related case worth naming. Where Airline A sells a flight, sub-charters it to Airline B, and B sub-charters to Airline C, the aeroplane operator is C — the entity actually conducting the flight under its AOC.
Chains of this kind are common in cargo and ad-hoc charter. Each link should confirm attribution in writing, and the operator at the end of the chain is often the one least connected to the fuel arrangements. Notification of any sub-charter should be a contractual requirement at every link, which is why it belongs in the lease clause set out in who reports CORSIA emissions for a leased aircraft.
For threshold consequences see CORSIA scope and thresholds; for multi-entity structures, CORSIA across a group with three AOCs. The operator definition is in the ICAO CORSIA implementation elements, and lease categories are described by IATA.
Frequently Asked Questions
Who reports CORSIA emissions on a wet lease?
The lessor, because the flight is conducted under the lessor's AOC with the lessor's crew. The marketing carrier that sold the flight has no CORSIA obligation for those sectors.
How is a damp lease treated for CORSIA?
By following the AOC. Damp lease is a commercial description rather than a regulatory category, and arrangements vary — the aeroplane operator is whichever entity's AOC authorises the flight, which the operations approval will make clear.
Does wet-leasing out capacity reduce my CORSIA obligation?
No. If the flights are conducted under your AOC with your crew, the emissions remain yours regardless of who sold the tickets. ACMI operators carry the full emissions of every sector flown for every customer.
What if the lessee arranges and pays for the fuel?
The lessor still reports, so the contract must require the lessee to provide per-uplift records monthly in a defined format, with retention and a right to request after termination. Without that clause the reporting party has no access to its own required data.
How should short-term wet leases be handled?
Confirm in writing before the first flight which party is the aeroplane operator, agree the fuel data flow in the same document, have the lessor's crew record fuel on board in the technical log as a backstop, capture uplift dockets at the point of uplift, and reconcile when the arrangement ends.
Who reports in a sub-charter chain?
The operator at the end of the chain — the entity actually conducting the flight under its own AOC. Every link should confirm attribution in writing, and notification of any sub-charter should be contractually required throughout.
Planning your CORSIA position? DSTechnoverse provides CORSIA carbon credit services for Indian operators and project developers — scope and readiness assessment, monitoring plans, data pipelines, verification support, unit sourcing and second-phase modelling. We are based in Indore, Madhya Pradesh and work across India.
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