French flag-carrier Air France said it expected its services to return to normal Friday after a four-day strike that saw hundreds of fights cancelled at airports across the country.

But the airline warned in a statement that there could be some delays as it worked to get its schedules back on track amid freezing conditions and snow in some parts of France.

Air France cancelled around a third of its long-haul flights and a quarter of shorter journeys every day since the start of the strike Monday by aviation workers.

The strike by pilots, flight attendants and ground staff was costing Air France eight to 10 million euros ($11-$13 million) per day, the company said.

Air France, the firm the worst hit by the industrial action, had urged customers to postpone travel and sent out tens of thousands of emails and text messages to clients warning them their flights had been cancelled or delayed.

The strike hit services at Paris's Charles de Gaulle airport, a global aviation hub, as well as several French regional airports.

Unions called the strike to protest against a draft law that would require aviation workers to individually give 48 hours notice prior to striking, saying this limits labour rights.

The bill was approved by France's lower house last month and is due to be debated in the Senate.

The head of the SNPL pilots' union, Yves Deshayes, said the union was to meet transport ministry officials on Friday and then decide whether to pursue further action against the bill.

But Transport Minister Thierry Mariani said the government would not drop the bill, which he said was aimed at protecting passengers' rights.