He said there was “simply no way for these cases to be determined without clarity” on European law points.

Aer Lingus, Ryanair, and Airlines for America — which represents US carriers — are challenging the Irish Aviation Authority’s (IAA) imposition of passenger caps at Dublin Airport for the winter and summer seasons.

Eoin McCullough, counsel for the authority, said that if the judge is satisfied with the facts outlined in the parties’ referral document, there may be no need for him to hear the challenges before the court gives its answers.

All of the cases had been due to be heard this week.

While taking into account the parties’ agreed wording, Mr Justice O’Donnell will decide the ultimate form of questions to be referred to the Luxembourg-based court, whose interpretation of European law is binding throughout member states.

He said he intends to make a final decision on the reference within a matter of days.

The proposed questions relate to interpretation of the EU’s slot regulation, which imposes rights and rules regarding airlines’ take-off and landing slots at European airports. The parties recommend asking, among other things, whether the slot regulation allows or requires the authority to take into account an imposed annual passenger cap when assessing the airport’s capacity.

Last month, Mr Justice O’Donnell granted an urgent pause to the effects of the authority’s decision to limit passenger numbers to 25.2m for the summer period, which runs from late March to October.

The move prevented the cap from being applied to a process of allocating the airport’s summer take-off and landing slots. His order is due to last until the High Court cases are resolved.

On Wednesday, Mr McCullough told the court it “may take some time” for the European court to rule, and the answers may not come until after the summer 2025 period has passed and his client has to make a further assessment of Dublin Airport’s capacity.

The parties may need to discuss what position should be taken while the EU court’s decision is pending, he said, adding that there could be a need to raise this with the court.

In deciding to impose winter and summer passenger caps, the authority said it considered technical, operational, environmental, and local planning constraints, including An Bord Pleanála’s imposition of a separate annual 32m passenger limit when it approved Terminal 2 in 2007.

The airlines claim there was no basis for the authority to have incorporated the 2007 planning condition in its assessment of the airport’s capacity. They said their right to certain legacy take-off and landing slots would be jeopardised if the summer cap took effect.

Daa has separately challenged the 14.4m seat cap for the winter period, which runs until March 2025, alleging it is not restrictive enough to prevent the airport from breaching the 2007 planning condition.The operator has said the EU slot regulation prohibits it from “unilaterally” reducing passenger numbers to comply with the planning condition. 

The Daa has separately applied to the local planning authority, Fingal County Council, seeking an increase of the 32m limit to 40m.