A first look at the CAA’s UK Aviation Environmental Review 2025: is UK aviation on track for Net Zero?

As we explained in our previous article in September 2025, the CAA is responsible for implementing the UK’s environmental reporting obligations, which it does through publishing the Aviation Environmental Review (the “AER”). In our previous article, we provided an overview of the CAA’s new approach towards the AER; now, just a few months later, we have the first example of how the CAA has put this approach into practice with the publication of its latest AER using data from up until 2024.

Read on below for our brief overview of CAP 3198 and what it can tell us about the state of UK aviation. 

1. What is the aim of environmental reporting, and how does the AER help achieve it?

As a carbon-intensive industry, aviation plays a crucial role in the UK’s efforts to meet its international environmental commitments. As we recognised in September, the AER provides an important tool for monitoring the industry’s performance with regard to the UK’s environmental objectives and for providing industry stakeholders with usable and detailed data.

2. What was the direction of travel in 2024?

CAP 3198 confirms that 2019 was the peak year for UK aviation in terms of flight numbers and CO2 emissions. The AER therefore uses 2019 aviation data as its benchmark for measuring performance. CAP 3198 also makes it clear that, if Net Zero is to be achieved by 2050, the baseline levels from 2019 cannot be exceeded. 

In terms of greenhouse gas emissions, noise pollution and air quality, road transport remains the largest contributor in the UK; for instance, 97% of greenhouse gas emissions are generated by road transport. Domestic civil aviation is, comparatively, a much smaller contributor at only 1%. However, emissions and pollution from road transport have fallen significantly overall. For example, from 2005 to 2023, emissions from passenger cars reduced by 23% despite the number of miles travelled increasing. A similar trend has been observed in the rail sector.

This is not the case for aviation. In 2024, emissions from UK flights grew faster than the number of flights. Accordingly, aviation is on track to become one of the highest-emitting sectors in the UK as other modes of transport decarbonise more quickly.

3. What about sustainable fuel?

Despite being one of the key areas identified in CAP 3153 for future reporting, the report does not include data on Sustainable Aviation Fuel (SAF). This is unsurprising given the historic nature of the data considered and accounting for the fact that the UK’s SAF Mandate has only recently come into force (see our overview of the SAF Mandate regime here). We can expect that it will take some time for the impact of SAF to filter through, and that the next edition of the AER will include more data on this point.

4. What does it mean for airlines?

The report uses a combination of pre-existing data sources and newly developed databases to analyse the emissions of aircraft departing the UK. The new database has greater accuracy by using the time spent actually in the air by each aircraft, rather than estimates, to measure emissions.

This allows the AER to provide more granular detail on aviation’s environmental impact. This includes greater transparency as to the relative environmental impacts of domestic and short-haul flights on the one hand, and medium-to-long-haul flights on the other. For example, the report confirms that while ultra-short and short-haul flights of under 1,500km account for 63% of all flights in the UK, they only account for 17% of total emissions. By contrast, long-haul flights are responsible for generating 63% of all emissions but represent the smallest proportion of flights in the UK (11%) overall.

It is possible that greater awareness in this area may lead to shifts in passenger behaviour and increased pressure for investment in more sustainable aircraft types and SAF. However, it is also possible that the increased transparency provided by the AER will provide new opportunities for airlines to strategically differentiate themselves in the market by improving resource efficiency and demonstrating leadership in sustainability.

5. What does it mean for airports?

The report includes detailed findings on air quality (broken down into NOx, SO2, PM2.5 and NMVOCS) and noise pollution around airports, which are individually named. 

The results of this analysis come as no surprise. They indicate that flights from the busiest 10 airports across the UK generate more than 95% of all emissions, with Heathrow alone generating more emissions than the other top 10 airports combined. 

There is positive news, however: while air traffic has not quite regained 2019 levels (94%), the level of noise pollution has actually fallen at a faster rate, leaving fewer people exposed to daytime aviation noise in 2024. Additionally, the level of SO2 emissions recorded across UK airports in 2023 was 67% lower than in 2019.

That notwithstanding, the air quality data reported in the AER suggests that other sectors are decarbonising more quickly than aviation. This may lead to increased scrutiny for the sector.

Next steps

The CAA is required to publish an AER at least every three years. We can therefore expect the next edition to be published by no later than December 2028. 

It will be interesting to see what story the next installment of data analysis tells us about the progress made by the industry following developments including the UK SAF Mandate, the increasing adoption of more fuel-efficient aircraft and the ongoing airspace modernisation programme. It will also be interesting to monitor whether the AER framework will account for other decarbonisation improvements across the sector, including the impact of the CAA's ongoing Hydrogen Challenge. This aims to increase sustainability by preparing UK aviation for the adoption of hydrogen as a zero-carbon fuel, both for use by new aircraft types (primarily on domestic regional routes) and within airport infrastructure.

This article was written by Patrick Bettle and Beata Kolodziej.

If you would like any further information, or advice related to any of the information in this article, please contact Chloe Challinor, Patrick Bettle or your usual contact within the Burges Salmon aviation team.