The first 24-hour shutdown by air traffic control chiefs began at 5am today, grounding a host of flights to and from France and southern Europe.
Ryanair bosses have cancelled 70 flights including services from Birmingham, East Midlands, Manchester and Stansted.
Services by British Airways, no-frills airline easyJet and Irish carrier Aer Lingus are also affected by the strike – sparked by a dispute over new labour laws.
France's largest air traffic control union, SNCTA, has threatened four more days of strikes next month.
Thomas Reynaert of Airlines for Europe said: "We are hurtling towards a summer of disruption and frustration for customers."
He added: "The overall impact of these strikes will be immense as they are taking place at a very busy time of the year."
A Ryanair spokesman last night told Daily Star Online: "Unfortunately, further flight delays and cancellations are likely.
"Ryanair sincerely apologises for any inconvenience caused by these unjustified disruptions which are entirely outside of our control."
A British Airways spokesman added: "We are sorry that customers are facing another potential day of delays and disruption."
