A strike by French air traffic controllers seeking better working conditions brought chaos at the height of Europe’s summer travel season after around 40% of flights to and from Paris were canceled on Friday.

Axar.az informs, citing AP, disruptions started hitting airports across France on Thursday. These intensified Friday as the national civil aviation authority asked airlines to cancel 40% of flights at Charles de Gaulle, Orly and Beauvais airports serving Paris, half of flights in Nice and 30% of flights in Marseille, Lyon and some other cities.

Despite the preventive cancelations, the authority warned in a statement that ″disruptions and long delays are to be expected at all French airports.”

Paris airports’ departure boards were showing a long list of flight delays and cancellations for destinations across France, Europe, North Africa and beyond.

Ryanair was among the airlines that announced widespread disruptions, saying in a statement that it had 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.

One of the two unions leading the strike, UNSA-ICNA, said in a statement there are not enough employees to handle surging air travel and that inflation is eating away at salaries. The unions are also protesting new reform measures aiming to more tightly monitor their work, prompted by a near-collision at the Bordeaux airport.

Transport Minister Philippe Tabarot called the unions’ demands — and their decision to strike just as French schools close for the summer and many families head on vacation — ″unacceptable.″