Pilots in Ireland, Ryanair's home country, held a strike for the first time on Thursday as they demanded better conditions from Europe's largest low-priced carrier, which is trying to stave off a wave of industrial action across its network.
"There has been no customer disruption other than the 30 flights which were cancelled ... and all these customers switched flights or selected refunds", a spokesman said.
But they have reassured passengers that all Ireland to Europe flights will operate as normal.
Some one hundred directly employed Ryanair pilots based in Ireland launched a 24-hour strike on Thursday after the airline's management failed to meet their demands during Wednesday talks.
The cancellations have arisen since 27% of Irish pilots of the Forsa union chose to strike and after conversations between the union and the airline proved fruitless.
The pilots' union Fórsa, of which the Irish Airline Pilots' Association (IALPA) is a branch, had earlier said it was not optimistic that a deal could be reached to avert the strike.
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That is just ahead of planned strikes by cabin crew in Spain Italy, Portugal and Belgium on 25 July and 26 July.
Ryanair has confirmed it has had to cancel a number of flights from Ireland as a 24hour pilot strike gets underway.
"We will do this by cancelling a number of flights on high frequency routes from Ireland to London and other United Kingdom destinations where customers can transfer readily to other flights".
The airline has said it "cannot rule out further disruptions in July and August".
However, Ryanair is facing further strikes in Spain, Portugal, Italy and Belgium later in the summer.
So far Ryanair haven't announced any more cancellations but the planned union strikes against the airline at other destinations across Europe are as follows.