RYANAIR's Irish-based pilots have said they will strike next week, just days before Christmas.
Pilots belonging to the Irish Airline Pilots' Association and the IMPACT trade union are to hold the one-day strike on Wednesday December 20.
IALPA which is a branch of IMPACT confirmed that it has served Ryanair management with notice of the strike action by Irish based directly employed pilots - most of whom are captains, without whom planes cannot fly.
IMPACT acknowledged that the move will either disrupt flights or generate substantial costs to the airline.
Yesterday, the Irish directly-employed pilots backed industrial action by 94%. However, the majority of Ryanair pilots who are contractors or hired through intermediary arrangements were not balloted.
IMPACT has warned of further strikes if agreement is not reached.
IMPACT official Ashley Connolly said Ryanair's failed negotiating model had let down both shareholders and tens of thousands of passengers, whose flights were cancelled this year - as "company-controlled" industrial relations proved incapable of recruiting and retaining enough pilots.
A number of aviation unions around Europe warned of imminent industrial action at Ryanair as pilots at the company intensify their campaign over negotiating and collective bargaining rights.
Italian pilots have already scheduled a four-hour stoppage between 1pm and 5pm this Friday and today, the German pilots' union Vereinigung Cockpit joined the campaign, warning that industrial action may spread to Ryanair pilots in Germany.
In a statement, Ryanair said it had received no notification of any industrial action by its German pilots, adding that it "suspect this is more PR activity by the Lufthansa pilots group VC."
"If any such action takes place, Ryanair will deal with it head on, but we will not deal with or recognise the Lufthansa pilots union VC, regardless of what action - if any - takes place," the statement added.
Meanwhile, Portuguese-based Ryanair pilots have also balloted for industrial action, but so far they have not served notice of industrial action.
Ryanair has threatened to withdraw recent pay rises and other benefits from pilots who refuse to negotiate through the negotiating structures preferred by management.