And the Irish trade union Impact said pilots in Ireland this week voted for a day of industrial action on December 20 that will mostly involve captains.
Italian pilots have already scheduled a four hour stoppage between 1pm and 5pm on Friday.
"Ryanair will not recognise an Aer Lingus pilot union, no matter how often or long this tiny minority (earning between €150,000 to €190,000 p.a.) try to disrupt our flights or customers' plans during Christmas week". "We see no other way", Vereinigung Cockpit president Ilja Schulz told reporters in Frankfurt.
Ryanair pilots want to replace what is known as employee representative councils with a collective bargaining system that would, in turn, take responsibility for all negotiations with the company right across Europe. Chief Executive Officer Michael O'Leary has repeatedly fought employees' attempts to gain union representation.
PILOTS employed directly by Ryanair in Dublin, its second largest base, have voted in favour of taking industrial action. According to Schulz, 95 percent of pilots who voted at the carrier's home base in Dublin and other Irish sites favored labor action.
The Cockpit union said that walkouts in Germany can be expected "any time starting immediately" but didn't give any specific timing.
Vereinigung Cockpit said it won't strike during from the afternoon of December 23 through December 26, the height of the Christmas holiday travel period.
The airline, which employs a total of about 360 pilots in Dublin, has refused to recognise a European Employee Representative Council established to represent Ryanair bases across the Continent, says the Irish Independent.
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".
Ryanair said in a statement: "Ryanair will deal with any such disruptions if, or when they arise, and we apologise sincerely to customers for any upset or worry this threatened action by less than 28 per cent of our Dublin pilots may cause them over the coming days". A crew shortage in September partly stemmed from rivals including Norwegian Air poaching its pilots. The company has offered higher pay and expanded hiring but has said it will reverse course on concessions if the pilots in Dublin strike.