Hundreds of flights have been cancelled as French air-traffic controllers join a national strike by public sector workers in France.

The USAC-CGT union said its members would strike from Monday evening to Wednesday morning “for the defence of public service,” adding: “We must resist the erosion of human rights.”

French air-traffic control (ATC) handles more flights than any other country in Europe, due to the size of the country and the fact that many aircraft traverse its territory between northern Europe, the Mediterranean and the Iberian peninsula.

A “Notice to Airmen” issued by the DGAC, the French aviation authority, said: “ATC capacity will be determined according to available staff.”

Airlines serving Paris Orly, Lyon and Marseille airports have already been told to cut one in five flights.

Ryanair, the biggest budget airline in Europe, made dozens of cancellations on Sunday evening once it became clear that the strike was going ahead.

The airline said: “Due to yet another French ATC strike, Ryanair regrets to inform customers that it has been forced to cancel a number of flights on Tuesday 22 May.

“All affected customers have been contacted by email and text message and advised of their options: a full refund, rebooking on to the next available flight or free transfer to an alternative flight.

”Due to this unjustified ATC strike action, we also expect delays to flights to/from/over France and we advise customers due to travel on Tuesday to check the status of their flight on the Ryanair.com website.”

Under European passengers’ rights rules, passengers are entitled to meals and accommodation until they can be flown to their destination — which may be on another airline if Ryanair has no availability on the day of travel or the following day.

No cash compensation is payable.

British Airways has cancelled at least 36 flights on Tuesday, connecting London with France, Spain, Switzerland and Italy.

Barcelona is worst affected, with three round-trips from Heathrow cancelled. Two return journeys to each of Madrid, Marseille, Paris CDG and Geneva have been cancelled.

The airline said: “We are unfortunately expecting a day of industrial action by air traffic controllers, as part of wider general strike in France on Tuesday 22 May.

“We will be using larger aircraft, where possible, to help affected customers and are doing all we can to reduce the levels of disruption.

“We recognise that you may not wish to travel as a result. We have therefore introduced a more flexible rebooking policy to help customers travel on alternative dates and avoid the strike action.”

Anyone who bought a BA ticket before 18 May to or from any French airport as well as Barcelona and Madrid on a British Airways-operated flight on Tuesday 22 May can switch to Monday, Wednesday or Thursday, “regardless of whether their flight is operating or not”.

Air France is also allowing passengers booked on Tuesday to travel instead on any day up to Friday. The French carrier has suffered months of disruption in a pay dispute with pilots, ground staff and cabin crew.

Sixty per cent of all easyJet flights traverse French airspace. The airline said: “We expect that there will be delays and cancellations due to the industrial action, therefore we advise all customers to check the status of their flight.

“Please also be aware that public transport services will be affected by the strike. We recommend all customers allow plenty of extra time to get to the airport and consider alternative transport options where possible.”