Air traffic controllers have voted 99% in favour of industrial action in a dispute over staffing.
A dozen flights were cancelled at Shannon Airport last night after controllers refused to work overtime.
The IMPACT Union said discussions will now take place on what form industrial action should take.
Controllers and the Irish Aviation Authority are scheduled to return to talks at the Labour Relations Commission on Tuesday week.
The Irish Aviation Authority has said it is disappointed that air traffic controllers have voted in favour of industrial action.
The authority said such action is breach of partnership agreement.
Meanwhile, management at Aer Lingus has told the Craft Group of Trade Unions that it will impose cost cutting measures in two week's time.
The union, which represents 180 engineering workers, pulled out of talks on Friday.
