1. CORSIA - background and objective

Througout the recent years, the climate-relevant emissions from air traffic have continuously risen with the growth of the sector. In response to this increase, the International Civil Aviation Organization (ICAO) set the goal to keep the overall amount of CO2 emissions from international air traffic stable, from 2020 onwards.

As a result, a global, market-based scheme with the objective to limit CO2 emissions caused by international air traffic was agreed on, in October, 2016 by the members of ICAO. This scheme is called CORSIA for short. CORSIA stands for Carbon Offsetting and Reduction Scheme for International Aviation.

In order to ensure the stagnation of aviation emissions in the future, various measures will be applied. On the one hand, this concerns improvements in aircraft technology …

… (turbines, aerodynamics etc.), on the other hand it is about operational improvements (e.g. routing). Furthermore, the use of sustainable aviation fuels is already in early test phases.

Lastly, CO2 emissions from international flights are also to be offset with so-called recognized project credits and with emission allowances from existing emissions trading systems. The aim is to achieve a CO2-neutral growth in international air traffic from 2020.

2. Who is obliged to participate in CORSIA?

All aircraft operators who use aircrafts on their international flights with a maximum take-off mass (MTOW) of more than 5,700 kg and who emit annual CO2 emissions of more than 10,000 tonnes are within the scope of CORSIA.

In the EU, the requirements of CORSIA were implemented in the European Emissions Trading System by means of a delegated regulation of the EU Commission (EU 2019/1603 of July 18, 2019).

  • The delegated regulation applies to aircraft operators who have an air operator certificate issued in an EEA state (including the outermost regions and the overseas territories and protected areas of this EEA state) and
  • which have been generating annual CO2 emissions of more than 10,000 tonnes since January 1, 2019 from aircrafts with a take-off mass of more than 5,700 kg.
  • The following flights are considered:
    – Flights that connect airports in different EEA countries or flights that connect airports in EEA countries with airports in other states;
    – international flights between airports in EEA countries and airports in the outermost regions or overseas territories, or protected areas in other EEA countries;
    – international flights between airports in the outermost regions as well as overseas territories or protected areas of EEA countries and airports in third countries or overseas territories or protected areas of other EEA countries.
  • Emissions from the following flights are excluded: State-mandated flights, humanitarian flights, medical flights, military flights and fire-fighting flights.
    These exceptions also apply within CORSIA in general. They also include the flights that took place before or after a humanitarian, medical or fire-fighting flight, if these were necessary to carry out purpose or to reposition aircrafts afterwards.

3. What is CORSIA and which regulations are relevant?

In order to achieve the goal of climate-neutral growth from 2020, several sets of rules have been created by the ICAO: The Standards and Recommended Practices (SARP). They were decided by the ICAO Council on June 27th, 2018 and have been in effect since January 1st, 2019. The CORSIA-SARP are also formally referred to as ICAO Annex 16 Volume IV.

The SARP include administrative requirements, monitoring, reporting and verification rules (MRV rules) and the calculation of the amount of compensation obligations.

The corresponding Environmental Technical Manual (ETM _prodecures for demonstration compliance with the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA)) provides assistance on the application of the SARP. It is not legally binding, but contains detailed background information on CORSIA requirements and explanatory practical examples. In addition there are five so-called CORSIA Implementation Elements:

  • CORSIA Chapter 3 States
    This contains a list of the countries participating in CORSIA that are to be included in the route-based emissions calculations starting from 2021. They are updated annually.
  • CORSIA CO2 Estimation and Reporting Tool (ICAO CORSIA CERT)
    It provides simplified monitoring, reporting and verification (MRV) procedures.
  • CORSIA eligible fuels
    This document contains information on reducing CO2 emissions using CORSIA-approved fuels.
  • CORSIA eligible emission units
    This document contains criteria for issuing units and programs for eligible issuing units.
    This register contains information that must be made available to allow CORSIA to be implemented world wide (annual updates of the data on total CO2 emissions, from 2025 update of information on emission units and compliance with them every three years).

They are elements referred to in the SARP.

4. How does CORSIA work?

Aircraft operators from all ICAO member states – regardless of whether the state is participating in CORSIA – have been obliged to monitor their CO2 emissions since January 1st, 2019. This happens based on a monitoring plan, which must be applied after approval of the competent authority. The emissions determined therein are used as sectoral baseline. It is used to determine the average of the total CO2 emissions that shall be offset through CORSIA in a certain year after 2020.

The monitoring plan must contain the identification of the aircraft operator, the fleet- and operational data, the methods for calculating emissions from international flights and the information on data management and control.

In stage 1 (until 2026), the formula for calculating the compensation amount takes into account the growth of the entire aviation industry. This means that all emissions that occur in the period from 2021 to 2026 and that exceed the average of the 2019 emissions must be offset. Compensation can be done by using sustainable fuels or by deletion of a corresponding number of emission credits (the so-called offsets). The earlier mentioned SARP set the rules for deleting the offsets. In contrast to the European Emissions Trading System, not all aircraft emissions are offset. However, there is no free allocation of emission credits.

In stage 2 (starting from 2027) the growth of the individual emissions of each aircraft operator determines the calculation of the compensation.


Operators based outside the EU, can find the rules for monitoring and reporting in the Environmental Technical Manual (Doc 9501), Volume IV – Procedure for Proof of Compliance with the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).


For aircraft operators within the EU, the rules for the monitoring of the Implementing Regulation (EU) 2012/601 apply (see above). Since 2021, the update of this regulation, that was adopted in the end of 2018 applies: (EU) 2018/2066. In it, the EU Commission is adapting the existing monitoring rules of the EU-ETS for aircraft operators to make a joint monitoring and reporting under CORSIA and the EU-ETS possible. The monitoring plan always is the basis for reporting. It is coordinated between the aircraft operator and the competent authority and ultimately has to be approved by the authority.

During the examination of the annual emissions report, the verification bodies must confirm that aircraft operators are monitoring its emissions in accordance with their monitoring plans. If significant changes to the monitoring procedures are made, the monitoring plan must be resubmitted to the competent authority for approval.
The earlier mentioned ICAO CORSIA CO2 Estimation and Reporting Tool (CERT) was developed to simplify the monitoring process. With it the annual CO2 emissions of aircraft operators that emit only little amounts of emissions can be estimated. Furthermore, the ICAO CERT can be used by all other aircraft operators to provisionally estimate their own emissions and to close data gaps in the reporting (see also Resolution A39-3 of the ICAO Assembly).

  • Besides the use of bespoken ICAO CERT, operators can also monitor emissions by tracking their fuel use, applying one of five recognized methods (see “Fuel Use Monitoring Methods” below). Afterwards, the CO2 emissions are to be
  • calculated.

An aircraft operator’s emission level determines whether the operator is entitled to use the ICAO CORSIA CERT or whether an individual method must be used, to monitor the fuel consumption. Each operator must select a suitable method (see below) and include the selection in the emissions monitoring plan.

Emission thresholds:

  • < 500 kt CO2/a from international flights in the period 2019-2020: Operators can use the ICAO CORSIA CERT to estimate and report the CO2 emissions.
  • > 500 kt CO2/a or equal to 500 kt CO2/a from international flights in the period 2019-2020: The operator must choose one of the five possible fuel use monitoring methods.

With the start of stage one (2021), the threshold for the eligibility to use the ICAO CORSIA CERT will change. It will then be< 50 kt CO2/a. In addition, operators can use the ICAO CORSIA CERT to estimate and report CO2 emissions that are not covered by compensation requirements.

The ICAO CORSIA CERT furthermore provides aircraft operators with standardized templates for monitoring plans and emissions reports. In particular, these are

  • the assessment of operator’s eligibility for using ICAO CORSIA CERT (Annex 16, Volume IV, Part II, Chapter 2, 2.2);
  • the assessment of whether the operator is within the scope of the MRV requirements from Chapter 2 or not; and
  • the closing of data gaps on CO2 emissions.

The five fuel use monitoring methods are described in Appendix 16, Volume IV, Appendix 2 and in the Environmental Technical Manual (Doc 9501), Volume IV – Procedures for demonstrating compliance with the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). An overview:

  • “Method A”
    Method A is based on the amount of fuel in the aircraft’s tanks immediately after refueling, as well as the amount of fuel, which is used during a flight. This method requires data from the flight under consideration (N) as well as from the subsequent flight (N + 1).
  • “Method B”
    Method B is based on the amount of fuel at the on-block time and the amount of fuel used during a flight. This method requires data from the flight to be considered (N) and data from the previous flight (N-1).
  • “Block-off / Block-on method”
    This method only requires data from the flight involved in the measurement. The fuel calculation refers to the fuel quantities at off-block and on-block. These data points are usually recorded in all aircraft operations for safety reasons.
  • “Fuel Uplift”
    The fuel quantities to be recorded for this method are only those, which are refueled. A particular challenge of this method is the allocation of the fuel if airplanes are refueled for more than one flight at once.
  • “Fuel Allocation with Block Hour”
    With this method, the total amount of fuel an aircraft operator has refueled is divided by all flights using of the block times. Both, aircraft types and fuel quantities per flight route must then be taken into account.

(According to the delegated regulation (EU) 2019/1603 only methods A and B are applicable for aircraft operators of the EEA states.)
From the ICAO’s point of view, these five methods are equivalent for the application of CORSIA and reflect established practices. That’s why ICAO gives aircraft operators the possibility to choose the method, that best fits the existing methods for recording the fuel consumption.
An aircraft operator can use different methods of monitoring fuel consumption for different types of aircraft in its fleet. If an aircraft operator wants to change a monitoring method, he must indicate the change in the monitoring plan and have it approved by the relevant authority.


For European aircraft operators, CORSIA reporting, the emissions report for the European Emissions Trading System and the verification report by the verification body can be issued together, on March 31 of the following year.


Verified emissions reports are to be submitted annually at the same time as the verification reports to the verification body to the responsible government agency. Both the operator and the verification body submit independently their reports.

The following deadlines apply:

  • 2019 and 2020: May 31 of the following year
  • 2021 to 2035: April 30 of the following year.

The national authorities forward the emissions reports of all participating aircraft operators to the ICAO no later than three months after the submission deadline.


Participating in CORSIA, aircraft operators must meet their compensation requirements by deleting eligible emission units (see above) in an amount that corresponds to the total compensation requirements of the relevant reporting period.
The cancellation obligation can only be done with the use of emission units (eg offset certificates) that have been declared admissible after an evaluation procedure by the ICAO Council . The issue units are acquired on the market through purchase.
The CORSIA SARP define quality criteria for the evaluation of the emission units. These include:

  • Credits must represent additional emission reductions (additionality)
  • It must be ensured that the offsets used in CORSIA are not also counted in national target achievements of emissions reductions (avoidance of double counting).
  • Projects must not violate local / regional / national rules and should prove that social concerns and environmental requirements are taken into account (e.g. resettlements for dam projects).

Internationally supervised offset programs such as the Clean Development Mechanism (CDM) and future market mechanisms under the Paris Agreement are applicable. The same is valid for voluntary standards under the supervision of the private organizations (such as The Gold Standard or VERRA) or national offset programs (such as American Carbon Registry). An ICAO working group checks the suitability for use under CORSIA on the basis of defined quality criteria. The permissible offset emission units are published regularly by the ICAO.

From 2021, operators can reduce their CORSIA compensation requirements by claiming emission reductions from the use of sustainable fuels that are permitted in CORSIA. For this purpose, requirements are defined which regulate the use of the so-called CORSIA eligible fuels (e.g. necessity of purchase records, use of life cycle emission values, definition of emission reduction factors for every CORSIA-compatible fuel, valid sustainability certificate). So far, only the criteria for evaluating fuels have been published by the ICAO. A list of the permitted certification schemes for fuels has not yet been published.

At the EU level, the list of emission units that can be used under CORSIA still needs to be transposed into European law.

The first deletion of emission units by aircraft operators will take place no later than January 31, 2025. For this purpose, aircraft operators submit a verified deletion report to the competent state authority. After verification, it will be forwarded to the ICAO.

5. Our offer

The Müller-BBM Cert Umweltgutachter GmbH is accredited by the German Accreditation Service (DAkkS) for checking CORSIA emission reports and is approved by the ICAO for the verification of the same (list of verification bodies).

Our accreditation for European Emissions Trading according to DIN EN ISO 14065 and VO (EU) 2018/2067 also includes the verification of CORSIA-relevant emissions for aircraft operators from the EEA area.

Our verifications are effective and individually adapted to the needs of each of our customers. By combining different auditing techniques, we ensure an efficient audit. Our verifications include the effectiveness of your control systems, an analytical test of the logical integrity of your data, a reasonable number of random samples to ensure the systematic integrity of your report and a comparison with flight plan data. We are happy to offer you this profoundness in combination with the convenience of a flawless workflow for your emissions reporting.

Our fundamentals include competence, customer orientation, independence and reliability. They always stand in the focus of our verification activities.

Are you looking for a partner for your CORSIA verification? Or would you like to acquire more information?

We will be happy to make an appointment to explain our offer and / or clarify your questions about CORSIA and carbon offsetting.

You can also call us directly at:

We offer you the full scope of the required verification services and can look back on more than 15 years of experience from European Emissions Trading – verifications. With our knowledge, we support you throughout the entire verification process, from the on-site audit up to the verification declaration.

If you would like to find out more about our company and our references, have a look over here:
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