Ryanair has cancelled 20 out of 300 flights to and from Dublin on Friday 3 August due to a strike.
The airline says all 3,500 affected customers have already been notified by email or text message.
It is due to a fourth day of industrial action by directly employed Dublin-based pilots on that day.
Speaking in Rome, Taoiseach (Irish prime minister) Leo Varadkar expressed concern over the impact of the ongoing Ryanair dispute.
'Come to agreement'
Mr Varadkar appealed to the airline and the union to consider how the industrial action is affecting "the people and the customers".
"They are the ones that pay the wages of the pilots and the cabin crew and ultimately pay the dividends of the shareholders and keep the board in office," he said.
"I would ask that they get around the table, come to an agreement and allow things to return to normal".
Ryanair management said all 50,000 passengers affected over the course of the strike had been given alternative flights or received refunds.