Ryanair has repeated its call for the European Commission to take action to prevent further air traffic control strikes and warned of a possible “summer of discontent” for travellers.

The plea came ahead of the tomorrow’s walk out by French air traffic controllers tomorrow, the fifth strike in two months, and the 46th in seven years.

Ryanair has been forced to cancel more than 70 flights on Thursday to and from and over France, with further delays likely.

The budget carrier advised customers travelling on Thursday to check the status of their flight on the Ryanair.com website before travelling to the airport.

It urged all those affected to sign its Keep Europe’s Skies Open petition, which it will present to the European Commission once it gains one million signatures.

Chief marketing officer, Kenny Jacobs, said: “Once more Europe’s consumers are being held to ransom by tiny French ATC unions, causing hundreds of thousands of passenger flights to be cancelled or delayed, while the European Commission and French government sit on their hands.

“As we approach the peak holiday season, European travellers should prepare for a summer of discontent as there is absolutely nothing preventing these selfish unions from staging even more strikes in the coming weeks and months.

“How many more flights and customers will be disrupted before the Commission finally takes action?”

Thomas Reynaert, managing director of lobby group Airlines for Europe, said: “2016 will be a record year for ATC strikes and there is nothing to stop further strike action this summer.

“We are shocked at yet another infringement of people’s rights.

“On behalf of European consumers we call on the European Commission and governments to act now and protect the rights of millions of European travellers affected by this repeated and disproportionate industrial action. They need to work to minimise the impact of strikes on passengers.”

Ryanair is putting discounted €19.99 fares on sale for 24 hours tomorrow to encourage the estimated 1.2 million Britons abroad to fly home and vote on the EU referendum on June 23. Tickets must be booked by midnight on Thursday for travel on June 22 or the voting day of June 23. The airline is actively backing the ‘remain’ campaign.