Airport ACA Program Changes: A Guide for Airports in Scope

The Airport Carbon Accreditation (ACA) program has introduced a major scope change for Level 3 and Level 3+ airports, requiring them to report Scope 3 full-flight emissions rather than just the Landing and Take-Off (LTO) cycle.

This update reflects the growing global emphasis on transparent, standardised sustainability reporting and aligns ACA requirements with the Greenhouse Gas (GHG) Protocol. While it helps close reporting gaps and support decarbonisation efforts, it also introduces new challenges in data collection, accuracy, and verification.

Our guide covers:

• What is the ACA Program Scope Change for Level 3 and 3+?
• Who Does ACA Scope Change apply to?
• How Does ACA Align with Global Standards?
• Adapting to ACA Program Updates: Practical Approaches and Common Challenges
• Key Milestones for the ACA Program
• How PACE Airports Can Help

What is the ACA Program Scope Change for Level 3 and 3+?

The Airport Carbon Accreditation (ACA) program, launched by Airports Council International (ACI) in 2009, is the only institutionally endorsed, global carbon management certification standard for airports. It recognises airports’ efforts to manage and reduce their carbon emissions across six progressive levels of certification – from mapping emissions to achieving net zero.

As sustainability reporting becomes more rigorous and standardised worldwide, airports are under mounting pressure to provide accurate, comprehensive data in a timely manner. This pressure has intensified with the latest ACA update, which requires Level 3 and Level 3+ accredited airports to report Scope 3 full-flight emissions – covering the entire flight from departure gate to arrival gate – rather than just the Landing and Take-Off (LTO) cycle.

This marks a significant shift in emissions accounting for airports, as Scope 3 full-flight emissions involve factors largely outside an airport’s direct control, including aircraft type, route length, and flight path.

Who Does ACA Scope Change apply to?

The change applies to any airport seeking to achieve or renew ACA Level 3 (Optimisation) or Level 3+ (Neutrality) accreditation.

ACA Accreditation Levels:

1. Level 1: Measure direct Scope 1 and 2 emissions.
2. Level 2: Demonstrate actual reductions in Scope 1 and 2.
3. Level 3: Account for Scope 3 emissions from third parties operating at the airport, now expanded to include full-flight.
4. Level 3+: Offset remaining direct emissions to achieve carbon neutrality.
5. Level 4: Integrate carbon management into long-term strategy.
6. Level 5: Achieve net zero, including Scope 3 full-flight emissions.

Accreditation is valid for one year from the date of certification. After one year, airports can either renew at the same level or move to a higher level.

Newly in-scope airports must make an early decision on the calculation methodology to use, as this will affect both immediate reporting and progression to Level 5, where a credible net-zero plan for Scope 3 full-flight emissions is mandatory.

How Does ACA Align with Global Standards?

The change directly aligns with Category 11 of the Greenhouse Gas (GHG) Protocol – “Use of Sold Products” – which covers emissions from the use of goods and services sold by a company. In the case of airports, this translates to the full-flight emissions associated with aircraft movements facilitated by the airport.

This alignment ensures consistency between ACA and widely recognised global carbon accounting frameworks, supporting international comparability and enabling airports to integrate ACA data into other mandatory and voluntary reporting schemes, such as:

• Task Force on Climate-related Financial Disclosures (TCFD) reporting.
• Corporate Sustainability Reporting Directive (CSRD) requirements in the EU.
• Science Based Targets initiative (SBTi) aviation pathways.

By harmonising with the GHG Protocol, the ACA update helps close reporting gaps between accreditation levels and strengthens the credibility of airports’ sustainability claims in the eyes of regulators, investors, and the travelling public.

Adapting to ACA Program Updates: Practical Approaches and Common Challenges

Method 1: Direct Flight Data from Airlines with In-House Tools
Some airports attempt to obtain detailed flight data directly from airlines and process it using custom-built emissions models.

Challenges:

• Data Access & Consistency: Securing granular flight data from airlines is often difficult. Even when data is shared, it typically arrives in varied formats, at inconsistent intervals, and with differing levels of detail—necessitating complex data transformation to normalise inputs.
• Emissions Factor Application: Applying appropriate emissions factors requires detailed knowledge of aircraft types and flight profiles. While tools like the ICAO Carbon Emissions Calculator exist, they do not cover all aircraft types and may lack the precision of commercial alternatives.
• Model Validation: Bespoke models tailored to individual airports often lack external validation, increasing the risk of undetected errors or miscalculations that could undermine reporting credibility.

Method 2: Fuel Uplift as a Proxy for Flight Emissions
Some airports have historically used fuel uplift data as a proxy for estimating aircraft emissions.

Challenges:

• Overstatement Risk: At larger hub airports, airlines may uplift fuel for multiple flights – which can lead to significant overstatement of emissions by the hub airport if fuel uplift is used as a source input.
• Understatement Risk: At regional airports, where aircraft often operate on short turnarounds without refuelling, emissions may be understated, potentially exposing the airport to greenwashing accusations.

PACE Findings
Analysis by PACE has shown that airports using fuel uplift as a proxy are typically overstating emissions by an amount equivalent to the second-largest airline operating at the airport. While overstatement may seem conservative, it complicates the development of a realistic net-zero pathway for ACA Level 5, effectively deferring the challenge rather than addressing it

Data Quality, Assurance, and Credibility

With full-flight emissions now in scope, the risk of inaccurate or unverifiable data increases. This can undermine stakeholder trust and lead to reputational damage.

Challenge:

• Limited internal expertise in emissions modelling.
• Difficulty obtaining third-party assurance for complex Scope 3 data.

Key Milestones for the ACA Program

• June 2009 – ACA officially launched by Airports Council International (ACI) Europe at its Annual Congress, becoming the first global carbon management standard for airports.
• December 2015 – At COP21 (Paris), ACI and UNFCCC announce partnership to promote airport carbon neutrality, with a target of 50 carbon-neutral airports by 2030.
• June 2017 – Commitment increased to 100 carbon-neutral airports by 2030.
• November 2024 –  ACA surpasses 600 accredited airports worldwide across all regions.
• December 6, 2023 – Level 5 Net Zero accreditation launched at COP28 in Dubai, certifying airports that achieve net-zero for Scope 1 and 2 and demonstrate robust plans for other emissions sources.
• August 2025 – Scope 3 Full-Flight Requirement Introduced for Level 3 and Level 3+ – airports must now report emissions for the entire flight (gate-to-gate), replacing the previous Landing and Take-Off (LTO)-only requirement. This aligns with Category 11 of the GHG Protocol and applies to all new and renewal applications from this date forward.

How PACE Airports Can Help

The PACE platform is purpose-built to help airports navigate these challenges. It supports multiple emissions frameworks, is compiled from a range of high-quality data sources, requiring minimal input from airports, and aligns with ACA and GHG Protocol requirements.

PACE enables airports to:

• Accurately calculate Scope 3 full-flight emissions.
• Normalise and validate complex datasets from airlines and third parties.
• Model net-zero pathways and prepare for ACA Level 5 certification.
• Avoid common pitfalls such as data inconsistency, overstatement, and underreporting.

The ACA program’s shift to full-flight emissions reporting reflects the aviation sector’s commitment to transparency and decarbonisation but also introduces new challenges for airports. As the aviation sector moves further towards more transparent and accountable sustainability practices, choosing the right tool is critical.

If your airport is preparing for ACA Level 3 or higher, or facing challenges with Scope 3 emissions reporting, PACE is here to help.