Leading airlines including Aer Lingus, Ryanair, and several American airlines challenged the IAA’s restrictive measure. They argued that the cap on seats would significantly impact their operations, particularly affecting their ability to retain crucial take-off and landing slots under the “use them or lose them” rule.

The seat limitation was established by the IAA with the aim of keeping the airport’s annual throughput under the maximum of 32 million passengers. This cap was a part of the 2007 planning permission agreement for the construction of Terminal Two.

This issue came to the forefront when Ryanair disclosed that Leinster Rugby would have to relocate departures for some of its away matches to Belfast due to the restrictions at Dublin Airport. The Dublin-based rugby team plans to use Belfast International Airport for four upcoming games unless the cap issue is resolved soon.

Moreover, a separate legal action concerning the IAA’s decision to also cap the winter passenger seats at 14.4 million is set to be reviewed in court this December. This action is jointly pursued by Aer Lingus, Ryanair, and the airport operator, DAA.

In his judgment, Mr. Justice O’Donnell highlighted that the adverse effects of not pausing the seat cap would extend far beyond the airlines. He emphasized that failing to grant a stay could lead to serious disruptions for the public and potentially damaging consequences for the wider economy.

Paul Sreenan SC, representing Aer Lingus, expressed urgent concerns in court last Friday, warning of a projected revenue loss of €84 million in 2024 and up to €130 million by 2026 if the cap remains. The cap could severely impact the airlines’ operations, particularly their “use them or lose them” policy for securing airport slots—critical assets that require utilization of 80% per season to retain for the following year.

This imminent court ruling follows a contentious IAA decision that sets a 25.2 million seat capacity for the summer, spanning late March to October. The authority had previously set a winter cap of 14.4 million seats, a decision that has also been met with legal challenges from Ryanair and the Dublin Airport Authority (DAA).

The DAA, on the other hand, has raised concerns that even the winter cap might be too high to stay within the annual limit of 32 million passengers—a figure mandated by An Bord Pleanála in 2007 when Terminal 2 was approved. They have also petitioned for an increase to 40 million passengers, citing planning constraints.

The crux of the airlines’ argument is that the IAA should not consider the 2007 planning condition when assessing capacity, a stance supported by Sreenan who emphasized that the focus should remain squarely on the allocation of slots. In contrast, the DAA contends that pausing the summer cap would facilitate breaches of planning conditions, potentially leading to enforcement actions against the airport authority.

The High Court’s decision could have far-reaching implications, not only for the airlines involved but also for the operational dynamics of Dublin Airport and its adherence to regulatory and environmental standards. As airlines and the airport authority await the ruling, the outcome is set to shape the strategic decisions of the aviation sector in Ireland for years to come.