Ryanair is bracing for its biggest-ever one-day strike on Friday (Aug 10) with pilots based in five European countries set to walk out, forcing the cancellation of about one in six of its daily flights at the height of the holiday season.
This includes 78 flights to or from Spain, a move that will affect 14,000 passengers.
The airline said the strikes were "regrettable and unjustified" and called for unions to come back to the negotiating table.
Germany will be the country most affected by the strike with 250 flight cancellations across ten airports. Previous year it agreed to recognise unions for the first time but it is in a dispute over collective labour agreements.
Anyone whose flight is expected to be disrupted will receive an email or SMS text advising them of the news, Ryanair said, with the status of individual flights able to be checked on its website.
Ryanair operates more than 2,000 flights a day, serving 223 airports across 37 countries in Europe and North Africa, and insists it will not change the low-priced model that transformed the industry and has made it Europe's most profitable airline.
In June Ryanair signed an agreement with the Unite union, giving hundreds of cabin crew employees full consultation rights and collective bargaining.
Unions also want the airline to give contractors the same work conditions as staff employees.
Ryanair claimed more than 2,000 flights would operate as normal on Friday.
Ryanair planes have a capacity of 189, meaning more than 74,000 passengers could be affected.
Ryanair's management claims to have offered a pay increase and to be open to further talks.
It has already threatened to move part of its Dublin fleet to Poland, which could cost 300 jobs, including 100 pilot positions.
Since the it first recognised unions in December 2017, walkouts have been staged multiple times by Ryanair staff in various countries.
But the "once in a lifetime experience" of being at her best friend Justine's wedding seems impossible now, after Ryanair cancelled her flight with two days' notice.
Peter Scherrer, deputy secretary general of the European Trade Union Confederation, said he welcomed today's cross-border show of unity by pilots.
"We want to again apologise to customers affected by this unnecessary disruption and we ask the striking unions to continue negotiations instead of calling anymore unjustified strikes".