Eight hundred and fifty Aer Lingus staff based at Shannon face job cutbacks following the decision to cut two transatlantic routes operating from the Co Clare airport.
At a stroke a third of the US-bound traffic has been cut and two of the eight A330s planes based at Shannon are being grounded.
It is the first sign of how last week's attacks in the US will impact directly on the local economy.
Mr Tom McInerney, general manager, corporate affairs, said the decision would have serious implications. "The overall bookings on the transatlantic routes are drastically down. It would be totally imprudent to continue with the existing flights," he said.
The Baltimore route was inaugurated almost a year ago to the day and even as recently as three weeks ago, assurances were being given by Mr Jack Foley, Aer Lingus vice-president, North America, that it and the Newark flights would be increased.
Mr McInerney said that beyond the flight cancellations, there were no further details on how the Shannon operations would be affected.
Staff were told about the announcement at a series of meetings yesterday afternoon.
Apart from the reduction in employee numbers, the loss of the routes will seriously affect Aer Rianta's revenue for the last quarter of the current year and next year. "The indication of further possible cutbacks is an additional worry," a spokesman said.
Mr Tadhg Kearney, Limerick Chamber of Commerce's spokesman on aviation affairs, said the situation was more serious than the 1991 Gulf War. "Americans just simply will not travel."
He added that the airport was likely to see other drastic cutbacks from its American operators, Continental and Delta.
But the decision was coming at the end of the tourist season. "We could still hope to salvage next year's tourism season."
The Clare TD, Mr Tony Killeen (FF), a former chairman of the Shannon Status Committee, said airlines now faced a challenge to meet the current crisis by dropping fares and developing winter charter routes. "Obviously there is no point in running empty planes so some of the cutbacks become inevitable. But I would be surprised if there are major job losses. I do not see how they could implement them."
