Only three of 84 pilots voted against the decision in the ballot, which covered directly employed rather than agency staff.
In a separate statement, Ryanair said about the German strike: "Ryanair has received no notification of any industrial action by its German pilots so we suspect this is more PR activity by the Lufthansa pilots group VC".
Ryanair said it will deal with any such disruptions "if, or when they arise" and said it wanted to "apologise sincerely" to passengers "for any upset or worry" the threatened action may cause them.
"Like any group of workers, Ryanair's very well paid pilots are free to join unions but, like every other multinational, Ryanair is also free - under both Irish and EU law - to decline to engage with unions".
The dispute regards Ryanair management's refusal to recognise, or negotiate with, the European Employee Representative Council (EERC) or IALPA as the sole, independent representative body for pilots working at the organisation.
Impact, which said it has made "repeated" attempts to open discussion with airline management in recent months, warned of further strikes if an agreement is not reached.
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Ryanair responded with a statement that said the pilots striking would likely "shortly leave Ryanair" and "don't care how much upset they cause colleagues or customers."
Irish-based pilots are holding the 24 hour stoppage just five days before Christmas, although there are reports that flights from Shannon won't be affected as pilots there have already agreed a new pay deal.
"Ryanair will not recognise an Aer Lingus pilot union, no matter how often or how long this tiny minority (earning between €150,000 to €190,000 p.a.) try to disrupt our flights or our customers plans during Christmas week". It confirmed some disruption may occur and threatened to remove agreed benefits from any flight crew who took part in the industrial action. The pilots taking action are directly employed by the company.
The dispute is about winning independent representation for pilots in the company, Impact said.
Italian pilots have already set dates for strike action, while Portuguese aviators have announced unspecified action.
The union's Ingolf Schumacher, said "most airlines offer better working conditions than Ryanair" explaining that Ryanair's many contract pilot's who are effectively self-employed don't enjoy the same pay and conditions as pilot's at other airlines. If the action goes ahead, it will be the first time flight crew at Ryanair have ever walked out on strike.