Pilots from the Irish Airline Pilots' Association backed the industrial action overwhelmingly during secret ballots.
Ryanair passengers heading home for Christmas are facing significant disruption to their plans after the airline's pilots in Dublin announced a one-day strike next week. "We see no other way", Vereinigung Cockpit president Ilja Schulz told reporters in Frankfurt.
However, pilots argue that this weakens their bargaining power and they want to negotiate collectively through a new joint European Employee Representative Council (EERC). Chief Executive Officer Michael O'Leary has repeatedly fought employees' attempts to gain union representation.
Labor leaders across Europe are making an aggressive unionization drive for better working conditions at Ryanair, challenging a low-priced business model that helped make the Irish company the region's biggest budget airline.
Italy-based pilots plan a four-hour strike this Friday, 15 December.
Impact said Ryanair was the only Irish-based airline that refused to recognise unions and the dispute was "solely about winning independent representation for pilots in the company".
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The German trade union promised to avoid striking over Christmas, from 23-26 December.
The Cockpit union said that walkouts in Germany can be expected "any time starting immediately" but didn't give any specific timing.
Ryanair has insisted that it will "deal with any such disruptions" if and when they arise and apologised to customers for any worry or upset the proposed strike action has caused.
Ashley Connolly, a union official, said: "Management's failed negotiating model has let down shareholders and tens of thousands of passengers whose flights were cancelled this year because company-controlled industrial relations proved incapable of recruiting and retaining enough pilots".
In a statement, the airline said there would be some disruption as a result of the strike, which it claimed would be confined to only a small group of pilots are working their notice and will shortly leave the airline. Employee poaching by rivals exacerbated the problem.
"Ryanair is surprised that IALPA has threatened to disrupt Christmas week travel when IALPA's own numbers confirm that it has the support of less than 28% of Ryanair's over 300 Dublin pilots and when Ryanair's Belfast, Cork and Shannon bases have already agreed these 20% pay deals".