Ryanair cabin staff in Belgium, Spain and Portugal called a three-day strike on Friday (24 June) over a pay dispute, which has caused several flight cancellations.
Staff in France and Italy are also expected to walk out over the weekend, while crews in Spain are set to strike again from 30 June to 02 July.
Workers for the Irish budget carrier are demanding better pay and working conditions in response to rising inflation, Reuters reported.
"Conditions are terrible," said Ricardo Penarroias, president of SNPVAC, the union behind the strike in Portugal. "A crew member is not even allowed to take a bottle of water on a flight," he told Reuters.
According to local news reports in Belgium, the most significant disruption will be at Charleroi Airport, where some 80 flights will likely be cancelled on Friday and Saturday. At Brussels Airport, about 10 cancellations per day are expected.
This follows a three-day strike by pilots and cabin crew at Brussels Airlines, the Belgian subsidiary of Lufthansa, which began Thursday (23 June) and is expected to cause more than 300 flight cancellations.
Meanwhile, 18 Ryanair flights have been cancelled between Brussels and cities in Spain, according to Spain's cabin staff union, USO.
The Ryanair strike action comes ahead for a similar move by British Airways workers at London Heathrow, and adds to the air travel disruption across Europe as airlines struggle to ramp up following pandemic lockdowns.