Ryanair has cancelled 190 of 2,400 scheduled flights this Friday (September 28).
About 30,000 passengers will be affected, who have been informed of the cancellation by text and email.
The disruption is due to strike action by unions in Spain, Belgium, Holland, Portugal, Italy and Germany.
The industrial action by Ryanair staff, which has been long-running, centres on working conditions.
Staff based in countries other than Ireland are unhappy that Ryanair has been employing them under Irish legislation, BBC News reports.
Ryanair’s Kenny Jacobs said the repeated strikes were damaging the airline’s business and 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… 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,” he said.
“When we can successfully do deals with unions in Ireland, the UK, Germany and Italy, why are some unions in Belgium, Holland and Spain not doing similar deals?”