Over 1 million passengers were affected by French air traffic strikes in early July, as airlines warn of potential for further summer chaos.

The boss of easyJet has said that recent French air traffic control strikes created “unacceptable challenges for customers and crew”.

Kenton Jarvis, chief executive of the budget airline, added that they were “extremely unhappy” with the strike action in early July, which landed airlines with “unexpected and significant costs”.

More than 1 million passengers were impacted by the walkout from French air traffic controllers on 3 and 4 July over working conditions, according to European aviation coordinator Eurocontrol.

EasyJet cancelled 660 flights due to the action, costing a total of £15 million (€17.3 million). French air traffic control has been the leading cause of delays for the carrier since the start of the summer.

The easyJet chief’s comments add to pressure from budget carrier Ryanair, which has labelled the strikes from air traffic controllers as “recreational”.

The airline accused air traffic control staff in France of wanting “time off” during the strike action on 3 and 4 July.

Jade Kirwan, Ryanair's communications director, told The Telegraph that some staff had continued to strike or had called in sick over the weekend, resulting in two more days of cancellations.

Ryanair is concerned that similar action and sickness claims could continue during the summer holidays, causing more travel chaos for passengers.

“What’s stopping French air traffic controllers from closing the EU skies again next week or the week after with more of these unjustified recreational strikes?” CEO Michael O’Leary said earlier this month. (Euronews)