Pilot union FORSA announced they would be striking on 10 August for the fifth time in recent months.
Meanwhile, Ryanair said it has agreed to nine of Forsa's 11 demands and that Forsa is repeatedly declining its invitations to meet.
Ryanair pilots based in Ireland are staging their fourth one-day stoppage today, in a deepening row about terms and conditions. "FORSA should now explain why another 3,500 Irish customers will have their flights and holidays next Friday 10 Aug disrupted when FORSA have refused not one, but two invitations to meet with Ryanair to resolve this dispute".
Ryanair has condemned this fifth strike as irresponsible and disruptive to the thousands of passengers who will be affected during this peak travel period.
Ryanair shares were down 0.2% at 12.98 euros by 1455 GMT, near two-year lows and well below the level hit in December, when it shocked the markets by ending 32 years of refusing to recognise unions.
The airline has blamed pilots from rival airline Aer Lingus who, it says, are using the strike to their advantage to cause the maximum damage to Ryanair.The airline said in a statement: "It is quite clear that this agenda is being driven by, amongst others, an Aer Lingus pilot, Captain Evan Cullen, who appears to be controlling the Forsa agenda".
The news comes hot on the heels of a major strike last week by Ryanair cabin crew in Spain, Belgium, Italy and Portugal, and another by Ireland-based pilots, that forced the cancellation of hundreds of flights. The move could result in the loss of over 100 pilots and more than 200 cabin crew jobs.
Ryanair cancelled 24 of around 2,300 daily flights after a second one-day strike by Irish pilots.
Founded 33 years ago in Dublin, the airline boasts lower costs per passenger than its competitors.
"We have examples such as Norwegian or easyJet, companies that hire their pilots based in Spain under the legislation of the country".