Workers at Shannon Airport have voted overwhelmingly in favour of industrial action following the announcement of planned job cuts.
Aer Lingus warned staff earlier this week of plans to axe more than 100 ground
handling jobs.
Members of SIPTU voted to take action if the airline did not enter into fair negotiations.
Jack O'Connor, SIPTU general president, called on Aer Lingus management to immediately withdraw its job cuts plan.
"If there are problems at Shannon we are committed to working with management to resolve them, but we will not accept unilateral action designed to cut the workforce by 50% without negotiation," he said.
Aer Lingus spokeswoman Grainne O'Malley said there would be no compulsory redundancies but voluntary packages would be offered to ground handling staff.
"We have 208 staff but are only operating nine flights out of Shannon and four of those are transit flights from Dublin," she said.
"We just have too many people."
Aer Lingus plans to introduce a new operating structure at Shannon and focus on its operations in Dublin. SIPTU officials are due to meet Aer Lingus staff next week.