A strike by French air traffic controllers entered its second day on Friday, leaving many passengers stranded at the start of Europe's peak travel season.

Ryanair was among airlines that announced widespread disruptions, saying in a statement it canceled more than 400 flights affecting 70,000 passengers. The company said the strike affects all its flights over French airspace, as well as traffic in and out of French airports, and urged the European Union to reform air traffic rules.

Airlines and France's transport minister has condemned the strikes as unacceptable, at the start of summer holidays.