France was set for a fresh day of protests over labour reforms on Thursday, in yet another challenge for the embattled government of President Francois Hollande.

The protests coincide with strikes by air traffic controllers that are expected to cause travel chaos for thousands of passengers.

For Hollande’s Socialist government, the priority is to prevent the protests by unions and students from turning violent, as they did last week.

Some reform-minded unions have given their support to proposed changes to France’s famously stringent labour laws, but tens of thousands of students and workers took to the streets a week ago, angry over plans to make it easier for struggling companies to fire workers.

Cars were burned in Paris and more than 30 people arrested as protesters clashed with police, who responded with tear gas.

A video of an officer punching a 15-year-old boy on the sidelines of a protest in the capital went viral and fuelled further anger.

Organisers have threatened an even bigger day of demonstrations on Thursday.

A battle is also raging within Hollande’s ruling Socialist party, with many on the left of the party fiercely opposed to the reforms, billed as a last-gasp attempt to boost France’s flailing economy before next year’s presidential election.

Hollande has vowed not to run again if he cannot put a dent in the country’s stubbornly high unemployment figures — long stuck at around 10 percent — and hoped the modest labour reforms would encourage firms to hire more people.

But pressure from the street and parliament’s back benches caused the government to water down the proposals so that they only apply to large firms.

A recent poll found that 58 percent of the French public still opposed the measures.

Labour Minister Myriam El Khomri said this week that she understood why “such a profoundly reformist text has raised questions and requires debate,” adding that “it is not a blank cheque for companies.”

Bosses are also unhappy, particularly over the removal of a cap on compensation paid for unfair dismissal, and the scrapping of plans that would have allowed small- and medium-sized companies to unilaterally introduce flexible working hours.

Parliament is set to vote on the reforms in late April or early May.

– Air travel chaos –

Meanwhile, aviation authorities told airlines to cancel 20 percent of their flights from Paris Orly airport on Thursday and a third of flights from Marseille as air traffic controllers went on strike again.

Paris Charles De Gaulle airport was not expected to be affected by the 36-hour walkout over job cuts and the lack of investment in new technology.

The Airlines for Europe lobby group said it was the 43rd strike by French air traffic controllers since 2009. It was due to end at 5am on Friday.

A strike last week disrupted travel plans for thousands of passengers as airlines were forced to cancel up to a third of flights.

The demonstrations are another challenge to Hollande’s authority, coming after he on Wednesday scrapped the constitutional reforms he proposed following the Paris attacks, including a plan to strip convicted terrorists of their French nationality.

In a blow to his faltering credibility, Hollande said an agreement between the two houses of parliament on the measures had proved impossible.