Shannon Airport opened a new pre-clearance facility for US-bound traffic this morning.
The new system means flights to the US will be treated in the same way as internal US flights.
This is the first time a facility of this kind has been put in place in Europe.
From today, travellers will pass through US customs and immigration before embarking on flights to the US. In the past, they had to go through customs at their destination in the US.
A spokeswoman for the airport said the new facilities will decrease the time passengers spend waiting to be processed by US authorities. "All passengers will arrive in America 'pre-cleared', meaning they won't have to wait on arrival," she said. "However, we haven't increased processing time in Shannon, so the whole timeframe has been shortened."
US Ambassador to Ireland Dan Rooney was on hand to cut the tape. He called it "an historic day for our airport and, indeed, a milestone moment in Irish-US relations".
Chief executive of Limerick Chamber of Commerce, Maria Kelly welcomed the "hugely significant" move. "We would hope to see an almost immediate improvement in the attitudes to the area from foreign investors now that this has been implemented. This is the first step in making the region a European hub for business and travel to the States".
However, she warned "it is vital that the necessary and required budget" was made available to those responsible for marketing the airport's services.
A similar facility is due to begin in Dublin Airport in November 2010.