Aer Lingus has confirmed that 63 members of its cabin crew will lose their jobs due to a reduction in the winter flight schedule.
A spokeswoman said the employees had been informed yesterday that their contracts would not be renewed.
The staff affected had all been on fixed-term contracts which had come to a "natural end", she said.
Most of those let go were Dublin based, with some also based in Cork. The average duration of the contracts concerned was two years, although some were shorter, the spokeswoman said.
A statement from Impact said 65 workers were affected - 56 in Dublin and nine in Cork.
Impact official Christina Carney said workers were "devastated" by the news.
"There is a lot of shock and anger at how they have been treated by the company, and the manner in which the news was broken to them has only added to the shock and anger they are feeling," she said.
"They have worked very hard for the company over the last number of years, in order to ensure that passengers return to Aer Lingus. They thought they had a long term career with Aer Lingus. Many of them have mortgages and are facing a very uncertain future now."
The union will meet to discuss the compulsory redundancies and alternative proposals they want to put to Aer Lingus. It also accused the firm of walking away from an agreement made in November 2008, which is says protected the employment of the temporary cabin crew.
Aer Lingus will cancel a number of long-haul services for the winter, including its Dublin to Washington and San Francisco flights from October 25th. The Shannon to Chicago flights ceased on September 1st.