An organisation representing US airlines has claimed the decision by the Irish aviation regulator to restrict slots at Dublin Airport this winter due to the passenger cap is a violation of the US-EU Open Skies Agreement.
Airlines for America has joined the legal action being taken against the Irish Aviation Authority (IAA) by airport operator daa, Ryanair and Aer Lingus as a notice party.
In a statement the trade association, which counts American Airlines, Delta, United, Soutwest and jetBlue among its members, said it wants to see the matter resolved.
"The decision from the IAA to apply a restriction on passenger numbers for operations at Dublin Airport is a violation of the US-EU Open Skies agreement," it said in a statement.
"The filing made today is part of our ongoing effort to urge all governments involved - the Irish government, the European Commission, and the US government - to urgently resolve this matter before irreparable damage is done not only to US airlines, but also to Dublin Airport and the Irish economy."
"Dublin Airport is a critical transatlantic link and economic gateway between the US and Europe."
Keith Glatz, SVP of International Affairs, Airlines for America added that it is "unfathomable" that the Irish Government would "abandon its treaty obligations to the United States and allow the passenger cap at DUB to continue."
"Given the strong and diverse ties between the US and Ireland across business, families and culture - it is mind boggling we even find ourselves in the current situation," he said.
"Any outcome that results in a reduction of service is not only detrimental to the travelers, shippers and economies of both of our countries, it also has potential implications to the overall US-Ireland relationship."
The parties have been given leave by the High Court to challenge a 7 May decision by the IAA to restrict to 14.4m the total number of passenger seats that will be made available by airlines using Dublin Airport over the winter season.
Daa has argued that the decision will result in it breaching the 32 million annual passenger cap at the airport.
The airline operator has warned that it is on course to breach the cap this year by up to 1m passengers.
On the other hand, Ryanair and Aer Lingus have argued that the decision is legally flawed and should be set aside.
They say it will impact negatively on their ability to provide winter services.
The case is set to be heard in full on 3 December.
News of the decision by Airlines for America to join the action, first reported by the Business Post, will place further pressure on the Government to act to have the cap lifted.
The US-EU Open Skies Agreement opened up all transatlantic routes to EU and US airlines, enabling them to fly between any point in the two territories.
