Aer Lingus is being threatened with all-out strikes after cabin crew voted in favour of a protest against cutbacks and changes to work shifts.
More than nine out of every 10 workers balloted backed industrial action as anger mounts over the actions of management.
Trade union Impact said all-out strike action is a "distinct possibility" which will be on the table during talks over the coming days.
The closure of a cabin crew base at Shannon - which employs 87 workers - and the outsourcing of transatlantic crew deepened the fall-out between employees and management.
Niall Shanahan, Impact spokesman, accused airline chiefs of refusing to engage with workers to resolve their differences.
"Essentially what management want to do is bully the staff into submission," he said.
"That's what has driven this ballot. The depth of feeling is now there to support industrial action, up to and including strike action."
Mr Shanahan said the 91% of cabin crew workers who voted in favour of industrial action gave union leaders a very strong mandate for a walkout.
There are almost 1,000 cabin crew at Aer Lingus, most of whom are members of Impact.
The union will make its decision in the days ahead about its next step in the worsening row.
An Aer Lingus spokeswoman said the airline had not received notice of industrial action and had no further comment to make.