A cabin crew strike at EasyJet and Ryanair saw 15 flights to and from Spain cancelled and 175 others delayed Saturday, as staff at the Irish airline announced 12 more days of stoppages.

The strike at the two low-cost airlines over pay and working conditions began as European schools started breaking up for the summer, creating headaches for both holidaymakers and the aviation sector.

By 1:00 pm (1100 GMT) on Saturday, 10 Ryanair and five EasyJet flights had been cancelled and 175 flights delayed, of which 123 Ryanair and 52 EasyJet, unions said in a statement.

The series of rolling strikes by Ryanair cabin crew in Spain -- where there are some 1,900 employees -- began on June 24, with EasyJet staff joining on Friday.

Ryanair's USO union rep said the new stoppages would take place in three four-day stretches: July 12 to 15, July 18 to 21, and July 25 to 28 at the 10 Spanish airports where Ryanair operates.

"After six days of strike and in view of the unwillingness of the company to listen to its staff and its preference for leaving thousands of passengers grounded rather than sitting down to negotiate an agreement under Spanish law, we have been forced to call new strike days," said USO's Lidia Arasanz.

She said the initial strike, which consisted of two three-day stretches, had seen "more than 200 flights cancelled and almost 1,000 delays", with the upcoming stoppages likely to create similar levels of disruption.

EasyJet crew have pledged to strike during the first three weekends of July to demand parity in working conditions in line with other European airlines.

The strikes are a headache for the aviation sector, which has struggled to recruit people after massive layoffs during the Covid-19 pandemic.

Meanwhile in France, dozens of flights were cancelled at Paris' Charles de Gaulle airport where firefighters have been on strike since Thursday, forcing the aviation authorities to close a number of runways as a preventative measure.

Between 7:00 am and 2:00 pm (0500-1200 GMT), one in five incoming or outgoing flights had been cancelled, airport operator ADP said.