Tens of thousands of passengers rearranged plans as more than 1,500 flights canceled following the French air traffic controllers’ strike in just two days. Workers’ demands for better working conditions led to the cancellation of around 40 percent of flights to and from Paris on July 4.

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 across Europe have canceled hundreds of flights on the second day of an air traffic controllers’ strike in France that’s causing chaos just as the busiest travel season of the year gets underway.