(Bloomberg) -- London Heathrow and Paris- Charles de Gaulle airports are cutting more flights as Europe’s travel chaos continues into the summer. 

Heathrow asked airlines to cut 30 flights from their schedules Thursday morning amid concern that peak passenger numbers will exceed the level it can safely handle.

France’s civil aviation authority has ordered a 17% reduction in flights out of Paris-Charles de Gaulle on Thursday due to a strike by firefighters. The walkout will lead to a shutdown of two out of the the hub’s four runways between 7 a.m. and 2 p.m. local time. The labor strife could continue into the weekend and spill over to Paris’s other hub at Orly, as more categories of workers plan walkouts. 

As a result of the disruptions Thursday, Air France-KLM’s French arm canceled 62 flights, while maintaining all of its long-haul and 90% of short and medium-haul connections, according to a spokesman. 

While the flights affected represent only a small portion of the total from the two airports, the last-minute cancellations add to the chaos surrounding travel in Europe as staffing shortages upend timetables and labor unrest gathers steam. 

Heathrow, Europe’s busiest prior to the coronavirus pandemic, will work with carriers to rebook passengers onto services outside peak hours so that as many as possible can still fly, it said in a statement Wednesday.

The scrapping of flights at Heathrow comes even after British Airways, the airport’s biggest carrier, slashed summer capacity 10% to reduce pressure on operations.

“We are working hard to ensure everyone has a smooth journey through Heathrow this summer,” the hub said. “The most important thing is to make sure that all service providers at the airport have enough resources to meet demand.”

At Paris-CDG, the country’s biggest international airport, the upheaval could get worse on Friday when a strike is planned by unions representing a broader swath of workers. 

Talks between operator Aeroports de Paris and labor representatives failed to reach a wage deal earlier this week, with staff demanding better compensation to reflect inflation and improved working conditions. 

(Adds details from Air France from fourth paragraph.)

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