Now is not the time to reduce ambition on tackling aviation emissions

In 2025, flights departing from European airports generated enough carbon emissions to surpass 2019 levels for the first time since the pandemic. Of these flights, almost a fifth came from UK airports and seven of the top ten most polluting flight routes in Europe originated from London.

This data - recently published as part of T&E’s report on European carbon pricing - provides a stark picture of the scale of emissions associated with UK departing flights. London to New York alone generates more carbon emissions than the annual tailpipe emissions of all cars in a city the size of Birmingham.

UK aviation emissions are rapidly increasing, and showing no sign of slowing. According to the Climate Change Committee, by 2040 aviation will be the primary source of emissions across all sectors of the UK economy. Airport expansion and an ever increasing number of flights is central to this assessment - T&E analysis suggests that the total number of flights departing the UK has now recovered to around 93% from the pre-pandemic period. The Government is also doubling down on London airport expansion, despite analysis suggesting we are approaching a point of saturation, where additional air connectivity no longer adds significant value to the capital. The aviation sector has rebuilt but without cleaning up.

Flights emissions are increasing but airlines are not being charged

The UK Emissions Trading Scheme (ETS) is a system designed to charge sectors such as aviation, power generation and energy intensive industries for the emissions they produce thereby driving the adoption of green emission cutting technologies.

However for aviation, the scheme does not cover flights that land outside of the UK, the European Economic Area or Gibraltar. Since these are long haul flights they are also the most polluting. Due to this large loophole, currently 83% of the emissions produced by UK departing flights are not covered by the ETS. This means that the aviation industry is paying for only a tiny fraction of the emissions that they produce, and the flights doing the most damage are precisely those the system does not reach.

The Government may weaken its ambition

Whilst aviation emissions rise and the industry continues to not be adequately taxed through the UK ETS, due to aviation industry lobbying the Government is now considering watering down the only piece of regulation which is set to cut aviation emissions. In December 2025, the Government launched a Call for Evidence to consider if crop based biofuels should be included in the UK SAF Mandate. This regulation requires an increasing proportion of sustainable aviation fuels that must be used by airlines every year.

At a time when aviation emissions are spiraling, including crop based biofuels in the UK SAF Mandate would be a major step down in ambition from the Government, for several reasons:

1. Crop based SAF has high carbon and sustainability risks. When accounting for the full lifecycle, including the carbon-intensive reality of indirect land use change, our research highlights that some crop-derived fuels can be up to 16% more carbon-intensive than standard jet fuel, once the displacement of food crops and subsequent deforestation are factored in. By allowing these feedstocks into the UK SAF Mandate, the Government would risk incentivising a fuel source that creates a net increase in carbon emissions, effectively widening the emissions gap that the UK ETS already fails to close. Currently, the UK SAF Mandate explicitly excludes these crops in favor of high-integrity alternatives like Power-to-Liquid (e-fuels) and waste based biofuels.
   
   

2. Crop based biofuels have limited potential to support the mandate. Globally, SAF production from sugar, starch, and oil crops remains constrained by production capacity and by strong competing demand such as from food or feed. In the UK, domestic crop-based potential is particularly limited. Crops currently grown domestically for road biofuels would translate into less than 1% of projected UK jet fuel demand in 2030. There is no sustainably “spare” crop capacity - diverting crops from road fuels to aviation would prevent land from returning to food production, thereby perpetuating indirect land-use change (ILUC) risks. Even for cover crops and crops grown on degraded or marginal land, domestic supply potential is incredibly small. At maximum, such pathways could supply around 3% of UK bio-SAF demand in 2030 and around 1% of the 2040 target, with significant uncertainties and monitoring challenges.
   
   

3. There are also significant competitiveness and trade risks. Including crop-based SAF would increase reliance on imports, particularly from the United States. UK-produced bioethanol is significantly more expensive than US supply and unlikely to be able to compete. UK bioethanol share in the road market has shrunk from ~20% in 2022 to ~10% in 2024 while the share of the US has grown from 29% to 60%. As a result, the SAF mandate risks becoming a channel for subsidised imports rather than a support mechanism for UK farmers or domestic industry.

As UK aviation emissions rise significantly - unchecked by any effective emissions trading scheme - the Government must resist industry pressure to weaken the crucial SAF Mandate.

Instead, it must keep the mandate focused on fuels like e-fuels and genuine wastes to drive meaningful decarbonisation. Including crop based biofuels in the mandate will undermine the world-leading steps the UK has made, at a time when reducing emissions from UK aviation has never been so important.

To find out more, download the briefing.