TRADE union SIPTU will again ask Aer Lingus workers to consider striking over a major pensions dispute.
The union has written to Aer Lingus, accusing it of "deliberately frustrating the resolution of the pension process by multiple means" and being "insulting and disingenuous".
It said it is "left with no option but to ballot for industrial action, up to and including a full withdrawal of labour to assist our objectives".
Aer Lingus's pensions troubles are well documented. Its retirement scheme, which serves thousands of current and former Aer Lingus and Dublin Airport Authority workers, carries a massive shortfall which hasn't yet been resolved by its trustees and the Pensions Board.
However, Goodbody Stockbrokers analyst Donal O'Neill urged caution in response to the news.
"I don't expect a big reaction in terms of ticket sales or share price," he said. "Strike threats are part and parcel of the aviation industry, they happen all the time.
"And balloting is just the first step. It's not yet clear whether the union actually has the legal mandate to strike."
Mr O'Neill said there had not been a strike at Aer Lingus in several years, despite threats. However, its regional service Aer Arann only narrowly avoided a strike earlier this month and talks are ongoing.