Beyond Compliance: How Your Flight Data Shapes Your Non-CO₂ Climate Impact

The landscape of aviation sustainability is undergoing a seismic shift. As of January 1, 2025, the European Union’s Emissions Trading System (EU ETS) mandates that airlines monitor and report their non-CO₂ climate impacts for flights within the European Economic Area. Scientific bodies like EASA and the IPCC have highlighted the urgency, revealing that non-CO₂ effects—primarily from contrails—can have a warming impact several times greater than that of CO₂.

This new regulation presents both a significant challenge and a massive opportunity. The key to navigating this new era lies in the data you use. Moving beyond passive compliance to strategic data management can dramatically change your reported climate impact. The foundational decision every airline must make is whether to rely on default secondary data or to leverage its own primary data.

While the EU’s reporting tool, NEATS, offers the option to use secondary data for ease of administration, this convenience comes at a cost. This data relies on “conservative” default values, which assume higher-impact scenarios and can lead to an overestimation of an airline’s climate impact by as much as 20-30%, depending on its operational region and fleet.

Primary data, on the other hand, is the actual, monitored information from your flight operations. While it requires a data collection process, the payoff is a report that accurately reflects your operations and gives you control over the outcome.

So, which specific parameters have the greatest influence? Let’s break down the science.

Decoding Your Impact: The Four Data Clusters

Your final non-CO₂ calculation is shaped by four distinct categories of data. Understanding them is the first step toward building an effective reporting strategy.

1. The Uncontrollable Element: Weather Contrails only form under specific atmospheric conditions known as ice-supersaturated regions, which are typically cold and humid. The EU’s reporting tool uses a standard weather model (DWD ICON) to identify these sensitive areas. While you cannot control the weather, you can control how you interact with it. For accurate reporting, knowing precisely where and when your aircraft flew in relation to these weather patterns is paramount.

2. Your Biggest Lever: Stochastic Operational Data This is where your primary data has the most significant influence. The single most important input you can provide is your actual four-dimensional flight trajectory. Instead of letting the reporting tool estimate your route, providing the precise path your aircraft took ensures the assessment is based on the actual atmospheric conditions it encountered. Other critical data points in this category include true air speed, engine efficiency, and actual fuel flow. The impact of this data is “stochastic”—it might increase or decrease your reported values for a specific flight, but it will always provide a more accurate reflection of your actual operations.

3. The Hidden Penalty: Conservative Defaults This is where relying on secondary data can be most detrimental. If you don’t provide specific primary data, the system will use default values that are designed to be conservative, often resulting in a higher reported impact. Two areas are particularly striking:

• Engine UID: The reporting tool assigns a default engine Unique Identifier (UID) for each aircraft type. However, different engines have vastly different soot emissions, which directly impacts contrail formation. For a Boeing 787, the default Trent 1000 engine results in an order of magnitude higher emissions in the model compared to the GEnx engine. Similarly, for an A320neo, the default Pratt & Whitney engine is modeled as a multiple-times-higher polluter than the LEAP engine. If your airline operates the more efficient engine but relies on the default, you are taking a compliance hit for better-performing equipment you are already using.
• Aircraft Weight (Load Factor): Without primary data, the system assumes the maximum takeoff weight for the aircraft. This dramatically inflates fuel burn calculations. In reality, there is a clear relationship between a lower load factor and reduced energy forcing from contrails. This sensitivity can be aircraft-dependent and, for certain flights, can create a sharp threshold where contrails suddenly form only after a specific load factor is reached.

4. The Nuances of Fuel Chemistry Fuel properties, whether conventional or sustainable, also play a critical role.

• Sustainable Aviation Fuel (SAF): Using SAF blends can significantly decrease soot emissions and therefore reduce contrail formation. However, this benefit is not automatic; it must be reported. The effectiveness of SAF can vary significantly by route, with some flights seeing an 80% reduction in contrail impact from a 50% blend, while others see a more modest effect. Strategically reporting SAF usage where it matters most is key.
• Conventional Fuel Properties: Even the specific chemistry of conventional jet fuel matters. Two key properties are its lower calorific value (the energy released) and its water emission index (the water vapor produced). A fuel with a higher energy content and lower water emission will form fewer contrails. While the average impact across all flights might be a 7% difference between the best- and worst-case fuels, for a specific flight this can be game-changing. In one extreme example shown in the webinar, a flight from Thailand to Manchester was so sensitive that simply choosing a fuel with better properties could have eliminated 70% of its total climate impact.

Key Takeaways for Your Reporting Strategy

As we move forward into this new regulatory environment, three principles should guide your approach:

1. Not All Parameters Are Equal. Your 4D flight trajectory, engine type, and aircraft weight will often have a much larger impact than other variables. Prioritizing the collection of these high-impact data points is the first step toward an effective strategy.
2. System Defaults Are a Hidden Disadvantage. Relying on the default values provided by reporting tools is the fastest way to have your emissions overestimated, potentially increasing your future liability.
3. Context is Everything. There is no one-size-fits-all solution. Your airline’s unique operational context—including typical routes, fleet composition, and regional weather patterns—determines your specific sensitivities. Understanding your own data is the only way to know where to focus your efforts.

The era of non-CO₂ reporting is here. By embracing a data-driven strategy, airlines can move from simply meeting compliance requirements to actively and accurately managing their climate impact.