Expansion plans at 20 of Europe’s largest airports are facing renewed criticism after an analysis by Transport & Environment concluded that the planned increase in flight and passenger numbers would cause every airport included in the study to exceed its fair share of the carbon budget associated with a 1.7°C warming pathway. The analysis covered airports in ten European countries, including airports in London, Paris, Madrid, Lisbon, Dublin, Frankfurt and Brussels.
According to the study, current growth plans would cause each airport’s carbon budget to be exceeded by between twofold and threefold. The organization also says that European aviation will consume its remaining budget for the 1.5°C pathway during 2026, while its budget for the 1.7°C pathway will be exhausted by 2033.
Growth cancels out efficiency gains
Airlines’ and airports’ arguments in favor of expansion are based on the view that the use of sustainable aviation fuel, together with improvements in aircraft and engine efficiency, could allow air traffic to increase without undermining European climate targets. But the T&E analysis concludes that the impact of increasing the number of flights, adding runways and expanding passenger terminals would cancel out those gains, even when higher use of sustainable aviation fuel and improved aircraft efficiency are taken into account.
Denise Auclair, head of the Travel Smart campaign at T&E, said that increasing the scale of air traffic by adding runways and expanding terminals would eliminate the benefits of cleaner fuels and more efficient engines, adding that the organization sees no realistic technological improvement capable of closing the gap within the required timeframe.
Examples from Portugal, Ireland and Spain
Expansion plans for Lisbon and Porto airports in Portugal record the largest exceedance in the analysis, at 2.8 times their allocated budget, followed by plans for Dublin Airport in Ireland at 2.6 times. The two Portuguese airports together account for around 80% of the country’s aviation emissions, and the study therefore says that keeping emissions within national limits would require reducing them by 12% annually rather than increasing capacity.
T&E estimates that the planned new airport in Lisbon could add 18 million tonnes of carbon dioxide, an amount equivalent to half a year of emissions from the entire Portuguese economy. In the United Kingdom, the additional impact of the third runway at Heathrow between 2035 and 2050 would equal a full year of emissions from Croatia’s economy.
As for Spain, the study says that aviation emissions there are growing faster than in any other major European country, despite simultaneous expansion plans for 12 airports. The airports of Madrid, Barcelona, Palma and Málaga accounted for 66% of emissions from departing flights in Spain during 2025, while their expansion could add 35 million tonnes of carbon dioxide. The expansion of Madrid alone is expected to add 23 million tonnes over 25 years, exceeding Spain’s total aviation emissions in 2025.
What changes in practice?
The analysis is significant because the national carbon budget is a shared resource among multiple sectors. If airports consume a larger share than permitted, industry, agriculture or heating will have to achieve additional reductions to compensate for that, according to T&E’s interpretation. The organization also warns of increasing legal risks for governments that approve expansions that may conflict with their climate commitments.
The organization is not proposing the creation of entirely new regulatory frameworks; it points to models in the United Kingdom and France for setting a national aviation budget or a decarbonization pathway that includes international flights, and to a Dutch model that establishes binding emissions limits at the airport level.
- Reject airport expansions when they exceed their fair share of carbon budgets, and establish a climate budget for each airport consistent with the Paris Agreement.
- End aviation tax exemptions, including imposing an appropriate tax on aviation fuel, applying value-added tax to tickets, and fully including international flights in the European emissions trading system.
- Align the number of takeoff and landing slots with climate limits, and reduce the most polluting and least socially valuable flights.
- Direct public funding, including European Investment Bank financing and state aid, toward cleaner transport alternatives instead of increasing airport capacity.
The editorial reading from certi.news
The source does not establish that every expansion project will be canceled or that the emissions estimates have independent consensus; it presents findings and analysis issued by T&E. But what is actually changing in the debate is the assessment standard: according to the study, aircraft efficiency or sustainable fuel alone is no longer sufficient if capacity and air traffic continue to grow. The full methodological details, including the assumptions concerning sustainable fuel use rates and the calculation of each airport’s fair share, still need to be reviewed in the original study before the findings are converted into final regulatory decisions.