Swords: Airport slot allocation may take account of an annual passenger limit written into an airport’s development consent, the Court of Justice has ruled. The judgment of 15 October 2026 in Case C-857/24 daa and Others settles a question that has worried airlines and airport operators across the Union.

The case concerns the Irish airport operator daa and a group of carriers. They disputed whether a coordinator may factor a passenger ceiling, set in the planning permission for terminal development, into the way runway slots are handed out. Airlines argued that EU slot rules look only at runway and terminal capacity declared under the slot regime, and that a planning cap should not narrow what they can claim.

The Court did not accept that reading. According to its press release, the passenger limit in a development consent can be considered when slots are allocated to airlines. That result lets national authorities and airport coordinators treat a binding planning condition as part of the real capacity of the site, rather than as a separate matter that sits outside the slot system.

The ruling matters for competition between carriers. Slots are the currency of aviation, and the rules decide who may fly at which hours from congested airports. If a passenger cap constrains the number of travellers, coordinators must decide how to share limited capacity between incumbents and new entrants. The judgment confirms that they may do so within the existing legal framework, although the Court’s summary leaves detailed allocation criteria to national courts and coordinators. Airport slot allocation therefore shapes fares and route choice as much as it shapes noise.

The decision also touches the balance between environmental and economic objectives. Passenger limits in planning permissions often exist to control noise, traffic and emissions around the airport. By accepting that such limits feed into airport slot allocation, the Court gives local planning decisions a practical effect on the market. Operators that wish to grow beyond a cap must seek a new consent rather than rely on the slot regime alone.

Airlines will read the judgment closely. Carriers that planned expansion at capped airports now face the prospect that coordinators will apply the limit when they assess slot requests. Operators, by contrast, gain legal certainty, because they can align the slot declaration with the conditions of their consent without fear that airport slot allocation will override it.

The Commission has been reviewing the Union’s slot rules for several years, and this ruling adds a point of reference to that work. Whatever reforms follow, the Court has made clear that airport slot allocation cannot ignore binding planning limits on passenger numbers. Airports, airlines and regulators now have to adapt their practice to that principle.