Ryanair says it is "disappointed" that the pilots union FORSA is threatening to go on strike during August.
Ryanair's pilots in Ireland have voted in favour of industrial action in their pay dispute.
Trade union Forsa said the action was backed by 94% of the 180 directly-employed pilots eligible to vote.
Forsa has said it will write to Ryanair's management team early next week to outline what it plans to do if pay demands are not met.
Meanwhile, the airline has shown its disappointment. Ryanair says less than 25% of its Irish pilots voted in favour.
In a statement, Ryanair said: "The result of FORSA’s ballot shows that less than half of Ryanair’s Irish pilots are members of FORSA, and less than 60% of these FORSA members participated in the ballot with less than 25% of Ryanair’s Irish Pilots voting for industrial action.
"This disruption of customers holiday plans has no valid mandate from Ryanair’s Irish Pilots."
Forsa said Ryanair had stalled on talks since the union submitted pay demands in March.
Ian McDonnell, Forsa’s assistant general secretary, said the pilots “are simply seeking pay levels that are common and competitive in the commercial airline sector”.
“They feel they have been forced into contemplating potentially-disruptive industrial action by a company that seems either unwilling or unable to negotiate in a professional and constructive manner,” McDonnell continued.
“At this stage, only a substantive counter-proposal, which properly addresses all areas of our claim, will be enough to prevent us serving notice of industrial action next week.”