Ryanair has cancelled 150 flights scheduled for Friday because of strikes by cabin crew in Spain, Belgium, the Netherlands, Portugal, Italy and Germany.
The flights represent 8% of the 2,400 originally scheduled.
The airline said in a statement that all affected customers have received emails or text messages informing them of the cancellation.
About 30,000 customers are likely to be affected out of 450,000 set to travel.