The airline has said up to 30 Irish flights will be cancelled tomorrow
The strike by Dublin-based pilots with Ryanair will go ahead tomorrow, after talks between the airline and the Fórsa union broke up this evening.
No substantive progress on the issues has been made following a day of talks.
Ryanair yesterday confirmed that it will cancel up to 30 flights between the UK and Ireland as a result of the industrial action.
Flights to mainland Europe will not be impacted.
Bernard Harbour, communications director with Fórsa, said: "There was no real optimism on either side that we could avoid tomorrow's industrial action - that's where we're at now this evening, so that will go ahead."
In a statement, the airline said: "Ryanair offered its pilots and Fórsa to set up a working group to explain and negotiate any issues arising from Ryanair's written proposals.
"Regrettably agreement on this sensible course of action wasn't possible after seven hours of talks."
Mr Harbour said that both sides were of the view that the working group proposal had potential, but "we were not able to agree on terms of reference".
Earlier, Ryanair said more than 90% of affected customers have either been re-accommodated on other flights or have applied for refunds.
Good news. By 5pm today, over 90% of our 5,000 customers whose Ireland-UK flights on Thur 12 July were cancelled due to an unnecessary strike by 27% of our Irish pilots will have been re-accommodated on alternative flights, or applied for full refunds.— Ryanair (@Ryanair) July 11, 2018
Tomorrow's strike is being organised by members of the Irish Air Line Pilots' Association (IALPA), which is a branch of the Fórsa union.
The dispute is around issues such as seniority, annual leave and base transfers.