Ryanair has cancelled 190 flights on Friday as cabin crew in Spain, Belgium, Holland, Portugal, Italy and Germany go on strike.
The flights represent eight per cent of the of the 2,400 scheduled departures on Friday.
All affected customers have received emails and text SMS messages from the carrier advising them of their flight cancellation.
“Ryanair sincerely regrets these unnecessary customer disruptions, which have been called by unions at the behest of competitor airline employees,” explained a statement.
Ryanair has made significant progress in recent weeks with its union negotiations, which include pilot and/or cabin crew agreements in Ireland, UK, Italy and Germany.
In the last two weeks, Ryanair has written to the pilot unions in Belgium, Holland, Spain, Portugal and Germany inviting them to negotiate similar agreements to that reached with FORSA in Ireland for both pilots and cabin crew.
Ryanair spokesman Kenny Jacobs said: “We sincerely apologise to those customers affected by these unnecessary strikes on Friday, which we have done our utmost to avoid, given that we have already offered these unions recognition agreements, collective labour agreements, and a move to local contracts and law in 2019.
“These repeated unnecessary strikes are damaging Ryanair’s business and our customer confidence at a time when oil prices are rising strongly, and if they continue, it is inevitable that we will have to look again at our capacity growth this winter and in summer 2019.
“We hope these unions will see common sense and work with us to finalise agreements for the benefit of our pilots and cabin crew over the coming weeks without further disrupting our customers or our flights.”
Some 30,000 passengers are likely to be impacted by the latest strikes.
Commenting on the cancellations Rory Boland, Which? travel editor, said: “These cancellations mean more travel chaos, more unnecessary disruption and more holiday plans in tatters for 30,000 Ryanair passengers – when will this airline finally do right by its customers?
“The airline must now immediately arrange alternative flights or provide a full refund and pay out compensation to those affected – including the many people still waiting for the money they’re owed from its shambolic summer of cancellations.”