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.

More than 1,500 flights have been cancelled on July 3-4, affecting nearly 300,000 passengers, due to a strike by French air traffic controllers, European industry lobby Airlines for Europe said in a statement.

Flights crossing France’s airspace, even those not destined for the country, faced delays and rerouting at the start of the summer vacation period.