Ryanair cabin crew in Spain, Portugal, Italy and Belgium are to hold strikes later this month.
Crews in all four countries will strike on July 25th, while crews in Portugal, Spain and Belgium will hold a further 24-hour strike on July 26th.
Unions say they are taking the action after Ryanair refused to meet a deadline for a series of demands over employment conditions.
"Regretfully, #Ryanair chose to continue to ignore its workforce and gave these Unions, no other choice but to call for a national 24 hours strike action in Portugal, Italy, Spain and Belgium for the 25th of July and in Portugal, Spain and Belgium for the 26th of July."
— CNE-GNC (@CNEGNC) July 5, 2018
In Dublin yesterday, cabin crew from across Europe issued a list of demands over pay and conditions - demands which the airline later dismissed as 'pointless'.
The latest developments come only days after Dublin-based pilots with the airline announced a one-day strike for July 12th.
Today, the airline's Irish pilots warned that their plans to strike next week still stand.
It comes after Ryanair appealed to them to call off the strike action.
Ryanair calls on FORSA to call off strike and meet: pic.twitter.com/aLWPY73Fwi
— Ryanair (@Ryanair) July 4, 2018
'Beyond anyone's understanding'
This afternoon, the Irish Airline Pilots Association (IALPA) warned that the strike action can only be avoided if agreement can be reached on 11 key demands.
The union warned that its members have seen "no evidence whatsoever on the part of Ryanair management to engage in meaningful negotiations with a view to reaching agreement on the issues they have presented to the company."
It said it is "completely at a loss to understand" the airline's surprise at the notice of strike action and said members are "and have always been" willing to meet the airline to resolve the dispute.
"We have consistently suggested a neutral venue which we will pay for and it is beyond anyone's understanding why you will not simply agree to this," the letter states.
"It is yet another example of a Ryanair view which is 'it's either our way or no way.'"
Pilots are demanding the introduction of a seniority system.
They have called for the introduction of a 'master list' on pilot seniority which would be used as basis for the distribution of entitlements like promotions, transfers and annual leave during school holidays.
Reporting by Stephen McNeice and Mick Staines