The aviation regulator has capped airline seat capacity in and out of Dublin airport for the forthcoming winter at 14.4m.
It is the first time that such a seat capacity limit has been put in place by the Irish Aviation Authority (IAA).
The decision comes as the airport hits the upper limit of a cap which limits the annual number of passengers who can use its facilities to 32m a year.
The cap was put in place as part of planning conditions for the second runway at the airport, which opened in August of 2022.
Last year, 31.9m passengers used the two terminals at the airport.
The IAA's decision will limit the ability of airlines to grow their routes and capacity at the airport between late October and the end of March.
The restrictions come despite airlines arguing that there should be no capacity limits related to the planning conditions, the IAA said.
Local residents, on the other hand, generally claimed that the conditions were a necessary constraint, the authority stated.
While the airport operator, daa, argued that the planning permissions limits should be reflected in the seat capacity decision, but did not propose how that should be done, the regulator added.
But the IAA said that having carefully considered the responses it received, it ultimately decided not to change its position from that contained in its draft decision published last month.
The various parties were among 70 individuals and organisations that responded to the IAA’s draft proposals.
Daa has applied to Fingal County Council for permission to increase the passenger cap to 40m a year.
The airport operators said it welcomed the IAA’s decision to establish a seat cap parameter for airlines granted slots to fly into Dublin Airport during the winter season as part of efforts to comply with the 32 million terminal passenger cap imposed on the airport.
But it also said that it believes there continues to be a significant risk that passenger numbers in 2024 will exceed the 32 million cap as additional measures daa proposed have not been accepted by the regulator in its final decision
"Dublin Airport is caught between a rock and a hard place," said daa CEO Kenny Jacobs.
"We want to continue to connect Ireland with the world, but we are also trying to comply with planning condition, even if the condition is less relevant then when decided almost 20 years ago."
"Pending the approval of our application to increase our passenger numbers to 40 million a year, we are making every effort to restrict growth to stay within the cap."
"The IAA has an important role in supporting this as it controls how many slots are allocated to airlines every year. At this stage, more action is necessary and we will work with the IAA and airlines so that any reductions are well managed."
In its submission on the draft decision last month, Aer Lingus argued that the IAA is not required to take account of the planning conditions when deciding capacity at the airport over the winter.
While Ryanair claimed that the proposed seat cap would artificially constrain capacity at the airport despite a €320m investment in the new north runway.
It said the cap would inevitably reduce connectivity and choice for Irish consumers.
