In May, the IAA announced a Passenger Air Traffic Movement (PATM) seat cap of just over 14.4 million passengers for Dublin Airport from October 27, 2024, to March 29, 2025.

The airlines argue that the decision is legally flawed and should be overturned.

They contend that the IAA exceeded its powers, acted outside its jurisdiction, and made an irrational decision. Additionally, they claim the IAA failed to provide proper reasons and violated various constitutional rights, including the airlines’ property rights.

The airport operator, DAA, has also filed its own High Court action against the IAA’s decision.

On Monday, Martin Hayden SC, representing Ryanair, and Paul Sreenan SC, representing Aer Lingus, informed the court that while both cases seek to overturn the IAA’s decision, they are based on different legal grounds compared to DAA’s action.

Mr. Sreenan stated that the decision would negatively impact Aer Lingus’ ability to offer certain winter services, such as flights for children to Lapland at Christmas and ski trips to France, Austria, and Switzerland.

Mr. Hayden expressed Ryanair’s concern that the decision could harm its business, especially if similar restrictions are applied for the Summer 2025 season. He estimated that another cap on passenger numbers could result in the loss of 5,600 slots or 1.1 million seats, potentially costing Ryanair up to €89 million.

The airlines seek to overturn the IAA’s decision and declare that the IAA erred in law and acted beyond its jurisdiction regarding the allocation of slots at EU airports by considering certain planning conditions of Dublin Airport’s Terminal 2 as relevant constraints.

DAA and Airport Coordination Limited, the appointed slot coordinator for Dublin Airport, are named as notice parties in the challenge.

Ms. Justice Niamh Hyland granted the airlines permission to bring their challenges on an ex-parte basis. She noted that both sides had the legal standing to pursue their actions, presented arguable grounds, and had no alternative means of challenging the decision other than judicial review.

The judge adjourned the airlines’ actions to a date next week. Counsel for the airlines expressed their hope that all three challenges against the IAA’s decision would be heard in succession by the same judge.