Comment on UK Government announcement of Gatwick Airport expansion by Professor Kevin Anderson and Dr. Lois Pennington, of Tyndall Centre, University of Manchester.
The UK Government has announced the expansion of Gatwick Airport, with passenger numbers expected to rise by around 40% within the next decade[1]. Ministers claim this will be “delivered in line with our legally binding climate change commitments and meet strict environmental requirements.”
The reality, however, is far from this. Expanding aviation capacity is fundamentally incompatible with the UK’s climate obligations under the UNFCCC [2], the Paris Agreement, and the Glasgow Climate Pact. The scale and urgency of emissions reductions needed to stay within 1.5°C, or even 2°C (see Box 1 below), of warming makes “sustainable aviation” a dangerous illusion [3].
Promises of efficiency gains and future technology cannot alter the physics. Aviation expansion drives emissions growth at exactly the moment when rapid reductions are essential. The immediate harms will fall disproportionately on poorer communities worldwide, many of them people of colour who seldom fly, while the medium-term damage will be borne by today’s children and generations to come.
This decision exposes a deliberate disregard for equity and intergenerational responsibility. It reflects a short-term political calculation, ignoring those without near-term voting power. No speech, no clever phrasing, and no appeal to future innovation can disguise the fact: by backing aviation expansion, the Transport Minister, the Chancellor, and the Prime Minister are betraying the very climate commitments they claim to uphold.
A Nation of Frequent Flyers
The UK makes up just 0.85% of the world’s population (2024), yet it has the third largest aviation market globally. In 2024, UK airports handled 261 million passengers, compared to a global total of around 5 billion. This means the UK accounted for more than 5% of all air passengers, that is around six times the global average per person [4].
The distributional implications are stark. A nation comprising less than 1% of the global population is appropriating aviation capacity at a level far out of proportion to its size, with the effects of the associated emissions externalised to the Global South. These are precisely the communities least responsible for climate change and least equipped to cope with its consequences. This is not just a statistical imbalance; it is systemic injustice.
Fairness and the Frequent Flyer Elite
Globally, around 11% of the population fly, with under 4% taking international flights. Even in wealthy nations like the UK, air travel is still dominated by a relatively small group of affluent frequent flyers [5]. Each year around half of UK citizens do not fly at all, while just 15% of the population account for 70% of all flights. Yet expansion is repeatedly framed and advertised as if it serves the “ordinary person.” This is a political and commercial trick: the benefits accrue to the few, while the costs fall on the many.
Investing in Gatwick expansion is a choice. It is a choice to prioritise frequent flyers over repairing the UK’s broken transport system, strengthening the NHS, or investing in climate resilience. More flights mean more emissions, worsening climate change for everyone. More flights mean more noise and disturbance for local communities, regardless of industry promises about each aircraft being a little quieter. And if future open-rotor designs are adopted (for their efficiency benefits), even the noise levels of individual aircraft could increase rather than decrease [6].
In short, aviation expansion entrenches privilege while deepening injustice both between and within countries.
The Mirage of Efficiency
Aviation’s first line of defence is efficiency. Yet the modern jet engine is already near the limits of thermodynamic design. Decades of world-class engineering have pushed its design as far as physics will reasonably allow, leaving no scope for further major gains. The same is true of aircraft designs. Within the constraints of today’s globalised aircraft industry, only incremental improvements remain possible.
The consequence is clear: over the next two decades, the UK and global fleets will look much like today’s. Concepts such as hydrogen aircraft or blended wing designs may have long-term potential, but they are entirely out of step with the short timelines dictated by international climate commitments (Box 1). Aviation is rightly safety-conscious and therefore is inherently conservative in adopting new technologies. The Boeing 747 entered service in the late 1960s and was still being produced in 2023. Despite many refinements, the essential design endured for over half a century, illustrating the slow pace of real change in this sector.
IATA’s own data confirms this stagnation. In 2019, global aviation fuel consumption averaged 4.2 litres per 100 passenger-kilometres [7]. By 2024, the figure was unchanged [8]. Efficiency had essentially flatlined. Meanwhile, the UK’s climate obligations demand double-digit emissions cuts year on year (Box 1). The gap between what efficiency can deliver and what science demands, if we aren’t to renege on our political climate commitments, is not marginal, it is absolute.
The False Promise of Sustainable Aviation Fuel (SAF)
Aviation’s second line of defence is SAF, promoted as a climate solution. The reality is sobering. Globally, aviation consumes around 375 billion litres [9] of kerosene each year. To align with 1.5°C, almost all of this would need to be replaced within a decade, or within two decades for 2°C. Seventeen years on from the first test flight using ‘biojet’ fuel, sustainable aviation fuel (SAF) still makes up only 0.7% of global jet fuel. In the UK, SAF is expected to reach just 2% of total jet fuel in 2025, assuming the SAF Mandate is met. That means more than 99% of jet fuel worldwide, and 98% in the UK, will still be fossil kerosene.
At present, the main feedstocks for Sustainable Aviation Fuels are used cooking oil, animal fats, and industrial greases, and these are expected to remain dominant for some years. Yet such resources are severely limited in supply, and aviation must compete for the same feedstocks with road transport and other sectors [10]. Beyond them, SAF production would need to rely increasingly on agricultural feedstocks, placing it in direct competition with food production at a time of rising global population and mounting climate impacts. As it stands, the UK’s SAF Mandate excludes fuels reliant on virgin agricultural feedstocks.
Finally, proponents of SAF and aviation expansion frequently highlight synthetic fuels as a prospective solution. While technically viable in principle, current production remains scarcely beyond the laboratory stage. Moreover, even at this early point it is evident that large-scale deployment would demand enormous energy inputs, casting significant doubt on both their feasibility and sustainability.
The rhetoric around SAF, often repeated by those promoting aviation expansion, may sound appealing. But once examined closely, the numbers and the underlying science reveal a very different story: not a breakthrough solution, rather another small technical fix being oversold as a meaningful response to the climate crisis.
With Gatwick’s expansion green-lit, passenger numbers are expected to grow by 40% in the next decade. The government’s SAF “growth plan” sets a target of 22% substitution by 2040. It is important to note that a switch to SAF does not eliminate lifecycle greenhouse gas emissions from jet fuel. As it is today, and according to the UK Government’s SAF Mandate, any SAF fuel used “must achieve a minimum GHG emissions reductions of 40%”, compared to kerosene. The Mandate goes on to suggest, “when fully replacing kerosene, SAF can achieve an average of over 70% greenhouse gas emissions savings on a lifecycle basis.” So even under a highly theoretical and complete substitution of kerosene for SAF, the aviation sector would still be releasing very high levels of greenhouse gases emissions.
As it stands, the proposed 22% of SAF by 2040, could represent no more than a 10% reduction in emissions – assuming no growth in demand. If that is the case, and set against an anticipated passenger growth of 40%, the actual level of Gatwick’s emissions is set to rise by between 20 and 30% by 2040 [11]. This is completely counter to the immediate, deep and rapid cuts in emissions necessary to deliver even the weakest interpretation of the Paris Agreement’s temperature commitments (Box1).
Another key issue is that if, as seems likely, the UK increases its reliance on SAF imports, this raises significant questions for other nations that face similarly pressing challenges in decarbonising aviation, alongside the rest of their economies, and all within just a decade or so. With Shell’s high-profile abandonment of its Netherlands biofuel plant, the prospect of producing genuinely sustainable SAF at a scale and within a meaningful timeline to replace kerosene look even more remote.
A final concern is that substituting it for kerosene will not eliminate the formation of contrails, the vapour trails left by aircraft[12]. The physics and chemistry behind contrail formation are complex, involving interactions between engine exhaust, atmospheric conditions, and ice crystal development. Their climate impact is also harder to quantify than the warming caused by burning fossil fuels directly. Nevertheless, research shows that contrails make a substantial contribution to aviation’s overall warming effect. Blending SAF with kerosene may help reduce soot and other contrail precursors, but much of the problem will remain largely unchecked.
The science is clear: climate change is driven by cumulative emissions. The challenge is not hitting distant targets but cutting emissions immediately and relentlessly until they reach zero. Delay today only makes future cuts steeper still and very quickly impossible. Enthusiastic promises about future SAF penetration or mid-century targets should not be mistaken for climate action. Without an immediate reduction in emissions, such claims are scientifically meaningless.
The Growth Illusion
Aviation is often defended as essential for economic growth. But the causal link is far from clear. Most, over 70% [13], of UK aviation is for leisure. In 2023, overseas tourists spent £31 billion in the UK. In the same year, UK residents spent £74 billion abroad. On balance, aviation drains more tourist wealth from the UK than it brings in [14].
Yes, aviation does support some international business links, but further expansion is unnecessary to sustain them [15]. Crucially, there is no robust evidence that investing material and labour resources in more aviation capacity delivers greater economic returns than investing in public services, infrastructure, or housing. In fact, aviation expansion appears to offer relatively poor economic value while generating clear social and health harms. By contrast, directing resources into UK infrastructure would provide far greater and more equitable benefits, while also reducing the significant net financial drain caused by outbound tourist spending.
Conclusion: A Choice About Who ‘We’ Are
Expanding Gatwick, and UK aviation more broadly, blows another huge hole in already perforated climate commitments. It is not a credible climate strategy, nor is it necessarily an economic one. It is a choice: to spend vast political, financial, and legal capital, not to mention skilled labour and resources on extending the privileges of a minority, while the costs in climate, health, and quality of life are borne by the many.
Imagine instead if that same effort and investment were channelled into modernising our crumbling transport networks, fixing the UK’s dilapidated housing, repairing run-down hospitals, and addressing fuel poverty in one of the richest nations on Earth. Surely this would be a much more equitable, sustainable and even economic way for the Chancellor to “get Britain building again”.
Aviation expansion is not about fairness, nor the economy, and certainly not the climate. Behind slick and carefully crafted headlines, it is about privilege; protecting the frequent-flyer advantages of the few, paid for by all, while sacrificing the many.
BOX 1: Summary of emission reduction rates necessary to deliver the Paris Agreement and Glasgow Climate Pact commitments of “pursuing” a temperature rise of no more than 1.5°C and remaining “well below 2°C”.
Using the carbon budgets from Lamboll et al (2023), it is possible to estimate the global reduction rates required for the 1.5°C and 2°C commitments. From the start of 2026, these are:
• For “pursuing ..1.5°C” (interpreted as a 50% chance): ~23% reduction year-on-year [16].
• For “well below 2°C” (interpreted as an 83% chance): ~8% reduction year-on-year.
These rates apply at the global level. However, in every international climate agreement since the UNFCCC in 1992, the UK and other signatories have endorsed the equity principle of Common but Differentiated Responsibilities and Respective Capabilities (CBDR-RC). This principle requires wealthy nations with high historical emissions to reduce faster than lower-income nations with little historical responsibility.
The collective failure of national leaders [17] to reverse the ongoing rise in global emissions has now rendered the 1.5°C commitment unattainable. In practice, the livelihoods, and in some cases the very lives, of poorer, climate-vulnerable communities have been sacrificed for continued economic growth in already wealthy nations and for high-carbon development in emerging and lower-income economies.
For the 2°C framing and adopting a relatively weak interpretation of the CBDR-RC principle, the required global reduction rate of 8% per year translates into annual cuts of 12 to 15% for the UK and many other wealthy nations [18].
When assessing whether airport expansion can be compatible with the UK’s climate commitments, this benchmark, a 12–15% annual reduction in emissions, should be regarded as the minimum threshold.
Endnotes:
[1] There are different ways to measure aviation activity. Passenger numbers are one straightforward metric; others include revenue passenger-kilometres (RPK) and available seat-kilometres (ASK), which better capture distance flown and seating capacity. While RPK and ASK can provide a fuller picture, they are often difficult to access at the national level and usually sit behind paywalls. Passenger numbers, by contrast, are widely available and are an adequate proxy of aviation demand, sufficient to clearly demonstrate the UK’s disproportionate level of flying.
[2] The United Nations Framework Convention on Climate Change
[3] These two episodes of the BBC radio programme Rethink provide a good headline summary of the issues: Episode 1- how can flying be less polluting? And Episode 2 – should we stop flying?
[4] In 2024 and at a global level, IATA estimate 5 billion passengers flew. In the same year UK airports saw passenger numbers reach 261 million. So, UK airports contributed 5.22% of all passengers flown. With the UK having 0.85% of the global population (in 2024), the level of flying (based on passenger numbers, see endnote 1) is around six times the global average.
[5] For further discussions of the equity issues in regard to flying see: How, ‘net zero’, sidelines equity when it comes to flying.
[6] There is a substantial body of research exploring ways to mitigate the higher noise levels associated with open-rotor engine designs, often by trading off a small amount of efficiency during non-cruise manoeuvres. Despite this, significant technical hurdles remain before open-rotor engines could match the noise performance of conventional jet engines with cased blades. It is also important to note that ongoing improvements to conventional designs would similarly yield incremental noise reductions. However, any marginal gains in noise reduction must be set against the wider context: plans for a major increase in flight frequency. Gatwick already operates under a generous allowance for night flights, which create considerable disturbance for surrounding communities. An expansion in operations would inevitably intensify these impacts, regardless of the specific engine technology employed.
[7] See table 7 of the IATA link provided in the text.
[8] This contrasts with the UK Government’s Climate Change Committee, who include a mean annual efficiency improvement in their balanced net zero pathway of 1.4%.(Table 3.7)
[9] IATA give the global consumption of jet fuel in 2024 at 99 billion US gallons, equivalent to 375 billion litres.
[10] As of today, the UK only has one SAF production facility, in Humberside. However, the SAF produced at the Phillips 66 plant doesn’t currently meet the specifications for it be CORSIA eligible. Other SAF plants are in the pipeline, but large-scale production remains some years away.
[11] This assumes that the planned for growth in passenger numbers broadly aligns with the rise in both passenger-kms travelled and the number of flights. It also assumes ongoing incremental improvements in efficiency.
[12] For a good explanation of the complexity of ‘contrails’, listen to: how can flying be less polluting
[13] In the absence of more recent data, this value is based on CAA data from 2018. There is little to suggest that the bounce back post-Covid has given a meaningful change in this estimate.
[14] This is premised on the working assumption that the proportion of UK tourists leaving the UK by plane is broadly similar to the proportion of foreign tourists entering the UK by plane.
[15] For two interesting discussions on this issue see: Losing Altitude, the economics of air transport in Great Britain and a report commissioned by the DfT, Wider Economic Impacts of Regional Air Connectivity
[16] A similar conclusion on necessary reduction rates was reached in a 2025 assessment from the UK Met Office, using a different method (CO2 concentrations rather than carbon budgets)
[17] This includes the UK. The headline claim, repeated by government and, regrettably, many experts, is that the UK has reduced its territorial emissions by 50% since 1990. Yet when emissions from international aviation, shipping, imports, and exports are included, the reduction is closer to 20%. That equates to an average annual reduction of less than 1% since 1990, far short of what is required globally, and even further from the level expected of the UK, ranked tenth in wealth, fourth in cumulative historical emissions, and with per-capita historical emissions around four times the global average.
[18] This is based on the method detailed in Factor of Two and updated to the start of 2026 using the Lamboll et al carbon budgets and assuming the emissions of 2025 will be the same as those of 2024.