Talks between SIPTU and Aer Lingus on the airline's latest cost-cutting plans have ended without any agreement at the Labour Relations Commission.
The discussions had been taking place for the past four weeks.
Aer Lingus has announced a €74m cost-cutting programme that would involve up to 1,500 job cuts through redundancy and outsourcing.
The airline says the cuts are needed to help it remain viable, but SIPTU has threatened industrial action if the move is implemented unilaterally.
In a statement last night, Aer Lingus accused the union of failing to engage in a meaningful way to produce an alternative set of proposals to the company's outsourcing plans.
It said it intended to finalise contract discussions with third-party suppliers by the end of next week.