Civil liberties groups have condemned a deal agreed this week between the European Commission and US Customs officials to share passenger information on transatlantic flights.
Under the agreement, airlines will be obliged to supply US officials with each passenger's name, itinerary, contact phone number and other details, such as credit card numbers, at least 15 minutes before each flight leaves Europe for the US.
The list of names will be checked against a US anti-terrorist database before each flight lands in the US.
The US deputy Customs commissioner, Mr Douglas Browning, has given Commission officials assurances about the "appropriate handling" of the data.
A spokesman for the Transport Commissioner, Ms Loyola de Palacio, said the arrangement satisfied US legal requirements while respecting European data protection laws.
"We were fully behind the Americans in their fight against terrorism and we wanted to promote co-operation and flexibility. Of course we have this very difficult legal situation. We think assurances given by the United States are sufficient on the law."
The new agreement, which comes into force on March 5th, is a transitional system and a permanent arrangement will have to be approved by EU governments and the European Parliament.
This week's agreement on exchanging passenger data comes after months of negotiations.
Commission officials say that, in the absence of a deal, Washington would have imposed new visa requirements on EU citizens travelling to the US.
Irish citizens travelling to the US on holidays or business for 90 days or less are currently allowed to enter the country without a visa, an arrangement that was felt to be under threat if the EU and US failed to reach an agreement.
The Irish Council for Civil Liberties said the agreement eroded privacy rights enjoyed by EU citizens under data protection laws.
Mr Liam Herrick said the agreement "will have a huge impact - besides these details, any information which the US Attorney General deems necessary can be requested", said Mr Herrick.
He said the biggest single danger was the absence of data protection in the US. "We've reasonably sophisticated data protection here but there is huge potential for this information to be shared among several US agencies such as the CIA, the FBI, Immigration and Tax services."
The Air Transport Users Council of the Chambers of Commerce of Ireland reacted with unease "at the overall thrust of the policy". Chairman Mr Tadhg Kearney said while they understood that post 9-11 there was a new context, they wondered if this response was proportionate.
"One suspects it is disproportionate. The EU have not asked for any reciprocal information from the US and one wonders will they be asking for such details from passengers on internal flights within the US," said Mr Kearney.