The continent's biggest lowcost carrier said it has cancelled 400 out of 2,400 European flights as pilots in Sweden, Ireland, Germany, Belgium and the Netherlands walked off the job. Twenty-two flights from Skavsta in Sweden have been grounded.
Ryanair said the strikes were "regretable and unjustified" and called for unions to return to the negotiating table. The Irish airline has offered customers refunds or the option of rerouting their journey on one of the busiest days of the summer holiday season.
Martin Lindgren from the union representing pilots in Sweden (SPF) told Swedish Radio that there are no plans to give up the struggle for the right to a contractual pension, sickness compensation and Swedish working time rules.
"We have not heard a word from Ryanair since they scheduled a negotiation this Tuesday. But we will not give up. If Ryanair continues to refuse to talk to us, there may be talk of new strikes or possibly legal action," said Martin Lindgren.