Despite the walkouts, 85pc of its scheduled flights, more than 2,000, will operate as normal, Ryanair said.
A spokesperson said: "Ryanair fully complies with all EU261 legislation, however as these flight cancellations were caused by extraordinary circumstances, no compensation is due.
For decades Ryanair has refused their employees basic labour rights most employees on the labour market take for granted, but here a strike is necessary to show the airline that it no longer can avoid treating its employees in a dignified manner", Martin Lindgren, President of the Swedish Pilots' Union, said in a statement. Irish pilots recently staged four one-day walkouts, while cabin crew in Spain, Belgium, Italy and Portugal went on strike on July 25 and 26.
Belgium-based Ryanair pilots gather at Charleroi Airport as part of a European-wide strike.
Ryanair, which flies in 37 countries and carried 130million people last year, averted widespread Christmas strikes last year by agreeing to recognise trade unions for the first time in its 33-year history.
Labour representatives are seeking collective bargaining agreements in the different countries.
But Ryanair pilots say they earn less than counterparts at other airlines such as Lufthansa.
Which flights are affected by the Ryanair strike?
Customers were notified as early as possible and a majority of those affected had already been moved to another Ryanair flight, the airline added.
Ingolf Schumacher, pay negotiator at Germany's Vereinigung Cockpit (VC) union, said pilots had to be prepared for "a very long battle" and that it could take months to push through change at Europe's largest low-priced carrier.
Around 55,000 passengers would be affected by the strikes, said Ryanair, which has offered customers refunds or the option of rerouting their journey.
But chief executive Michael O'Leary has also warned the airline may shift jobs and planes to more profitable areas if the turmoil continues.
Yesterday, at the eleventh hour, they were joined by Dutch pilots after an unsuccessful attempt by the airline to obtain a court order blocking the strike action.
Indonesia quake death toll almost triples to 347
Indonesia's chief security minister had earlier said 319 people had died, while local media have reported figures as high as 347. The official death toll from the initial quake stood at 321 as of Friday, according to Indonesia's mitigation agency (BNPB).
Liverpool finish pre-season with Torino canter
That combines with the £75m purchase of Virgil van Dijk in January as Liverpool look for their first ever Premier League title. Three minutes later, Wijnaldum rounded off a well-worked team move with a neat finish to double the hosts' lead.
Bright Conditions Promise Play On Day 2
Chris Woakes is expected to replace all-rounder Ben Stokes, who is standing trial in Bristol on a charge of affray. The play is set to start at the usual time of 11 a.m. with an extra 30 minutes to allowed at the end of the day.