This week's air traffic control strike in France saw more than 300 flight cancellations which will have caused delays and cancellations to the plans of some 200,000 travellers.
It is the 13th such strike this year alone and will not be the last. Another strike will take palce in Italy later this month and it is likely to see hundreds more flights affected.
Travellers, and travel managers, thought that the strikes would be over after two unions agreed a deal on pay and staffing in the sector but this week's strike is linked to labour reforms proposed by the French government.
Airline body Airlines 4 Europe, which includes Air France KLM, easyJet, Lufthansa and Ryanair among its members, says a recent analysis found that between 2010 and 2015 a total of 165 strike days had reduced European Union GDP by up to €9.5 billion.
The organisation said "The latest ATC strikes in Greece, Italy, Belgium and France since March this year caused over 3,500 cancellations among A4E members and more than one million minutes of delay (more than 16,000 hours) across all airlines operating in European airspace."
It says that ATC strikes occur most frequently in France, followed by Greece, Italy and Portugal.