SIPTU says a strike at Aer Lingus over St Patrick's weekend is now "highly likely".
The trade union has been locked in a pensions dispute with the airline and Dublin, Cork and Shannon airports.
The Minister for Transport, Leo Varadkar, has urged all sides to re-enter talks and avoid a strike.
"There is a solution … but it's going to require negotiations and a bit of give and take from both sides," he said.
"Strike action won't solve this problem. Renegotiation will."
The airline's CEO, Christoph Mueller, also echoed the sentiment that strike action will not help to settle the row, and said the airline cannot put off plans to improve their business any longer while they wait for it to be implemented.
The head of SIPTU's Pension Advisory Committee Dermot O'Loughlin says any strike would likely affect St Patrick's Day celebrations.