Union leaders have warned that any cost-cutting at Aer Lingus could put the chances of agreement at the national pay talks at risk.
It has been reported that the airline is planning to outsource up to 1,300 ground-handling staff.
Speaking ahead of today's pay talks session at Government Buildings, Siptu president Jack O'Connor said today such a plan would have "immense implications for the current talks process" and would "almost inevitably jeopardise any new national pay deal"
"Against the backdrop of any such large-scale cost-cutting proposals it would be very difficult for members to accept a new deal in a ballot," Mr O'Connor said.
Almost all ground operations staff at Aer Lingus are members of Siptu.
The general secretary of the Irish Congress of Trade Unions (Ictu) David Begg said the board of Aer Lingus has made "no decision" on costcutting proposals as outlined in the newspaper reports.
However, Mr Begg said it was "unavoidable" that the issue would be raised at the pay talks.
In addition to being the general secretary of Ictu, Mr Begg is also a member of the board of Aer Lingus.
The Impact trade union said it was not engaged in talks with management at the airline.
"Further to the recent announcement of a 'root and branch review' of the company's cost base, the union expects that proposals will be presented to staff by the end of September," a union spokesman said. "To date, no proposals have been presented and no negotiations have taken place.
The spokesman also rejected speculation that US-based cabin crew would fly on services to Ireland and then go back on return flights the same day.
"Impact would like to clarify that under internationally agreed standards, this practice would be unlawful," he said. A same-day return flight between New York and Dublin would constitute a minimum of an 18 hour working day for flight staff.
"International standards prohibit this type of practice in the interests of both workers and public safety," he said.