(Bloomberg) -- French aviation authorities warned of major travel disruptions as air-traffic controllers launch a protest campaign against work-rule changes ahead of the Summer Games in Paris. 

Airlines have been asked to reduce their flight schedules by 75% at Paris Orly airport on Thursday, by 55% at Charles-De Gaulle, 65% at Marseille and 45% at all other metropolitan airports, aviation authority DGAC said in a statement.

“Significant cancellations and delays are expected at all French airports” due to strikes and protests, France’s flagship airline said on its website. A detailed flight schedule will be published later Wednesday, the Air France-KLM unit said.

France’s air-traffic control unions are protesting the government’s effort to rewrite labor rules by including them among workers required to give strike notice in a timely manner. The dispute is raising concerns that travel disruptions could mar the run-up to the Olympic Games, set to kick off in Paris on July 26.

Sncta, the nation’s biggest air-traffic-control union, said Wednesday it had reached a deal to lift its strike notice, and backed away from a potential strike from May 9 to 11. Other strikes and protests remain in place, with “intense” talks ongoing, according to DGAC. 

Read more: Sporadic Strikes in France Are Causing European Flight Chaos

A series of  air-traffic control strikes roiled air travel across Europe last year, leading to thousands of cancellations and delays not only on flights to and from France but on other routes as well. That affected low-cost carriers like Ryanair Holdings Plc, which demanded the European Union do more to protect the industry in France.

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