A spokesperson said: "Despite regrettable and unjustified strike action taking place in 5 of our 37 markets on Friday (10 Aug), over 2,000 Ryanair flights (85% of our schedule) will operate as normal tomorrow carrying nearly 400,000 customers across Europe".
The airline says 85 per cent of its Friday flights would operate and that affected customers would get email or text messages later on Wednesday.
Customers have been notified and a majority of those affected moved to another Ryanair flight, the company said.
The airline said the strikes were "regrettable and unjustified" and called for unions to come back to the negotiating table.
In July, around 300 flights were cancelled in similar strikes in Portugal, Spain and Belgium.
A judge later ruled that Dutch pilots could join the strike.
Labour representatives are seeking collective bargaining agreements in the different countries. Ryanair had filed for an urgent court order to prevent industrial action by pilots in the Netherlands.
Aircrafts of low-priced airliner Ryanair are parked at the tarmac of Weeze airport near the German-Dutch border during a wider European strike of Ryanair airline crews to protest slow progress in negotiating a collective labour agreement at Weeze airport, Germany, August 10, 2018.More news: Sony’s Marvel Universe Updates: Silver and Black Splitting into Two & More
More news: Odds Slashed On Danny Welbeck Leaving Arsenal With Southampton, Everton In Frame
More news: Yerry Mina has explained his move to Everton on Deadline Day
The action is the largest in a series of strikes over pay and conditions.
Unions also want the airline to give contractors the same work conditions as staff employees.
Staff claim this creates huge insecurity for them, blocking their access to state benefits in their country. "It is annoying that it's happening in the holidays but that is the only means they have", said one man at an airport in Berlin.
Kenny Jacobs, Ryanair marketing director, called the strike "useless", and said that Ryanair pilots are paid better than their counterparts at competitor airlines Easyjet or Norwegian.
But chief executive Michael O'Leary has also warned the airline may shift jobs and planes to more profitable areas if the turmoil continues. The majority of customers affected have already been re-accommodated on another Ryanair flight.
Unions have strongly condemned what they see as Ryanair's attempts to play countries off against each other.
But some people took to Twitter to complain at how Ryanair handled the debacle after their flights were canceled.