Ryanair passengers face disruption to their Christmas travel plans after Pilots and crew announced industrial action in a bid to win union recognition and better conditions.
The airline, which does not recognise unions, said they represented about 28% of its Dublin-based captains.
Ryanair pilots and cabin crew in Germany, Italy and Portugal also plan action.
Cockpit, the German pilots' union, said its Ryanair members would strike for better pay and conditions if Ryanair failed to begin talks, but vowed not to disrupt flights over Christmas.
Ryanair said it would "not deal with or recognise" the German union "regardless of what action - if any - takes place".
Unions have long argued that their airline fails to offer pilots the same pay and conditions as its rivals.
Impact, the Irish pilots' union, said the dispute was "solely about winning independent representation for pilots in the company", said official Ashley Connolly.