Airlines and Dublin Airport are warning of possible disruption this weekend due to a strike in France.
Air traffic controllers are holding a 48-hour stoppage across tomorrow and Sunday.
Ahead of expected disruption, Ryanair has cancelled up to 100 of its European flights.
The airline is also expecting some significant delays to flights to France and routes using French airspace.
No Aer Lingus flights have been cancelled yet, but the airline said 16 are at risk of disruption.
The company said: "The strike is affecting airspace over the south-east of France. Nice, Marseilles and Lyon are the affected airports."
Dublin Airport, meanwhile, said some European flights to and from the airport have been cancelled.
A French air traffic control strike is scheduled to take place from 05.30 Sat 23 June until 05.30 Mon 25 June.
A number of European flights to/from @DublinAirport have been cancelled. Passengers are advised to check latest flight info with their airline before coming to airport.
— Dublin Airport (@DublinAirport) June 22, 2018
All passengers are being advised to check their flight status before travelling to the airport.
Explaining the situation, John Spollen - President of the Irish Travel Agents Association - said: "The air traffic control local to Marseilles have issues with rostering, and are going on strike.
"Previous strikes at that centre have resulted in cancellations and delays, as pilots flying to many of the Mediterranean destinations may take longer to get around the affected airspace."