(Luxembourg, 15 October 2026)
The Court of Justice of the European Union (CJEU) has today ruled that legal airport caps must be taken into consideration when determining annual traffic capacity. The ruling sets implications for the whole of Europe amidst industry pressure in Dublin to lift its airport’s passenger cap.
The Court has today confirmed that airport slots can be reduced under the EU Slot Regulation if there are constraints put in place, such as an annual passenger limit.
The aviation industry has long claimed that governments could not reduce slots at airports. Today’s ruling proves that to be incorrect and opens the door for governments to use slot allocation as a tool to reduce aviation’s climate impacts.
This ruling aligns with Opportunity Green’s legal analysis and the expert opinion we commissioned on these questions in October 2025. Our analysis also showed that broader climate-related measures, such as national carbon budgets, should also be relevant constraints if they affect airport infrastructure.
Olivia Moyle, Legal Officer at Opportunity Green, says:
“This ruling is an important step towards ensuring that airport capacity decisions are consistent with governments’ legal obligations. For too long, the aviation industry has argued that restrictions on airport capacity cannot be reflected in slot allocation. The Court’s decision provides much-needed clarity and reinforces the need to consider the legal constraints that apply to airports. Governments must now make full use of the legal tools available to address aviation’s climate impacts.”
The EU Slot Regulation provides Member States with general rules on airport slot allocation and reduction. Under consideration by the CJEU were three questions posed by the Irish High Court. These looked at whether the interpretation of ‘constraints’ that are considered when allocating annual airline slots extends to legal constraints placed on an airport.
In the case of Dublin Airport, a 32 million passenger cap per year limit is currently in place. Regardless of this restriction, the passenger limit has consistently been breached at Dublin Airport in 2023, 2024 and in 2025. In 2024, the Irish Aviation Authority (IAA), the independent state regulator, drew up coordination parameters under the Slot Regulation for winter (2024) and summer (2025). These included various measures to ensure that passenger numbers would not go beyond that 32 million limit. Following this move by the IAA the Dublin Airport Authority (daa), a semi-state commercial company that runs Dublin and Cork airports, and a number of airlines, lodged appeals before the High Court in Ireland.
In November 2024, the Irish High Court provisionally suspended implementation of the summer 2025 decision, which applied the passenger cap. This meant the airport coordinator was able to exceed the cap and allocate the air carriers all their historical slots for the season. Legal questions about the EU Slot Regulation were then referred to Europe’s top court.
The airlines – Aer Lingus, Ryanair and Airlines for America – submitted:
- First, that the limit of 32 million passengers a year is not a technical, operational or environmental constraint that must be taken into account in drawing up the coordination parameters.
- Second, that they had a right to ‘historical’ arrival and departure slots they had previously used at the airport”
Findings of the Court:
The CJEU rejected these arguments, confirming that all relevant technical, operational or environmental factors affecting airport capacity are not only physical or material factors but also legal constraints to the extent they affect the use of the airport. The judge went further to clarify that ‘all relevant’ factors is a broad term, and is therefore capable of encompassing a wide range of constraints, “whatever they may be”, regardless of whether they are political, legal or physical in nature, or whether they reflect measures which are long-standing or where there has been subsequent evolution. This supports Opportunity Green’s interpretation that broader climate provisions may constitute a relevant constraint for slot coordinators to account for when determining capacity at a coordinated airport.
In the given case, it found that compliance with the limit of 32 million passengers a year at Dublin Airport can be classified an operational constraint to be considered by the IAA when designating coordination parameters. The fact that the constraint in question comes from a State planning authority does not mean that it ceases to be an operational constraint.
The judges wholly rejected the airlines’ pleas in the domestic case regarding their rights to historical slots. Historical slots do not constitute property rights; instead they remain conditional on the authority’s authorisation and can therefore be removed pursuant to capacity
The CJEU has binding authority across all EU coordinated airports requiring allocation of slots. Capacity caps, or other binding airport legislation, must be heeded by coordinators. Contrary to the arguments raised by airlines in the Irish case, air carriers have no property rights to their previous slots and coordinators can remove these to curb emissions when they are mandated to do so.
The Court’s ruling is a positive step for climate action in aviation, providing important legal clarity for governments seeking to address aviation’s climate impacts. The decision has significant implications for how airport capacity decisions are approached in Ireland and across Europe at a time when aviation emissions are increasing. It clarifies how binding limits arising from Member States’ legal obligations must be considered under the EU Slot Regulation, with important implications for future action by Member States seeking to address aviation’s climate impacts.
Denise Auclair, head of T&E’s Travel Smart Campaign, says:
“Today’s ruling sets an important precedent in Europe: unchecked aviation growth is not exempt from the law, and governments across Europe now are empowered to use slot allocation to comply with legal obligations and reduce slots. This will have immediate implications for other countries where the aviation industry is attempting to avoid complying with legal obligations by challenging the relevance of airport capacity limits, such as in Belgium and Portugal.”
Dublin Airport’s passenger cap and climate obligations
This ruling sits within a complex chain of events relating to Dublin’s 32 million passenger cap. The Dublin Airport (Passenger Capacity) Bill 2026, enacted February 2026, gives the Minister for Transport the authority to amend or remove the airport’s passenger limit. The daa has formally requested that the Minister invokes the Bill to raise the cap, but this decision must be informed by an environmental impact assessment which considers the additional aircraft emissions from lifting the cap and how to mitigate them.
Sorcha Tunney, Senior Manager, Ireland, Opportunity Green, says:
“While the court’s ruling will not, in itself, prevent the Irish government from pursuing plans to remove Dublin Airport’s passenger cap, it clarifies the legal significance of airport capacity constraints. Removing the cap would enable increased airport activity, with significant implications for aviation emissions. The government cannot ignore the climate consequences of that decision. Across Europe, courts are increasingly recognising the responsibility of governments to address the harms from inadequate climate action to human rights and public health. Removing the cap without adequately addressing the resulting emissions could increase Ireland’s exposure to legal challenge under Article 8 of the European Convention on Human Rights (ECHR), which protects citizens’ fundamental rights.”
Louise O’Leary of Children’s Rights Over Flights says:
“Our children have seen their Minister for Climate working to increase polluting flights from Dublin Airport, instead of rapidly cutting aviation fossil fuel emissions – as their rights demand. The ECJ’s ruling is heartening but needs to result in actual enforcement of the passenger cap. We urge anyone who believes children’s welfare and future must be protected as the Climate Emergency worsens, to speak out against efforts to raise or remove responsible limits to passengers at Dublin Airport.”
ENDS
Notes to editors
What is the slot regulation?
The EU’s Slot Regulation (Regulation (EEC) 95/93), arrival and departure slots at coordinated EU airports are allocated twice yearly ‘while taking account of all relevant technical, operational and environmental constraints’ (Article 6(1)). Slots are allocated from a ‘slot pool’, and under the ‘use it or lose it’ rule, an airline may be entitled to the same series of slots if it has operated those slots for at least 80% of the time for which they have been allocated (also known as ‘historic slots’ and ‘grandfather rights’) (Article 8(2)).
What do we mean by ‘constraint’?
Under Article 6 of the Slot Regulation, when Member States are determining the parameters for slot allocation, they shall take account of ‘all relevant technical, operational and environmental constraints’.
This includes laws which impose a binding legal requirement to reduce airport capacity for environmental reasons, including climate change. Broader climate change-related limitations, such as national carbon budgets, that affect airport infrastructure may also fall within the scope of ‘constraint’ for the purposes of determining airport slots.