Aer Lingus management is proceeding with plans to cut 1,500 jobs at the airline after talks at the Labour Relations Commission broke down yesterday.
The airline is seeking cost savings of €74m by outsourcing up to 1,300 ground operations jobs, and using American crews on transatlantic routes.
SIPTU has warned that if Aer Lingus proceeds unilaterally with outsourcing, the union will in turn proceed with industrial action.
Aer Lingus wants to implement its controversial cost cuts on December 1. For four weeks, the Labour Relations Commission has tried to broker deal on alternative ways of securing the savings - but those talks collapsed yesterday.
Aer Lingus accused SIPTU of failing to engage in any meaningful way to address the cost base, adding that it can not afford further losses in 2009.
It has received proposals from outsourcing suppliers, and will select a preferred supplier by the end of next week - and then proceed to conclude contracts.
Staff will be advised of their redundancy options over the next fortnight.
SIPTU National Industrial Secretary Gerry McCormack accused Aer Lingus of walking out of the talks, adding that he was bitterly disappointed.
For passengers, there is renewed uncertainty about whether the threat of industrial action could disrupt travel plans in the weeks ahead.
The union's shop stewards will meet on Friday - and the staff ballot for industrial action concludes on Friday week.