Ryanair and Aer Lingus have cancelled more than two dozen flights to and from Ireland and France because of a strike by air traffic controllers there.
Further cancellations are likely.
Ryanair flights between Dublin and Madrid, Carcassone, Biarritz, Rodez, Nice and Nantes are among the flights affected along with flights between Cork and Bordeaux.
Aer Lingus has cancelled flights between Dublin and Barcelona, Madrid, Marseille, Perpignan, Nice and Bordeaux.
Both airlines are warning of delays to flights which need to use French airspace and are advising intending passengers to check their airline's website for updates.
It is the 12th strike by French air traffic controllers in the past 13 weeks in a protest against proposed labour reforms.