Airlines are advising passengers to check their websites for the status of their flights.
It comes as Ryanair cancel up to 168 flights, while Aer Lingus said their services are operating on long delays due to a strike by French air traffic controllers.
Thousands of Irish passengers' travel plans have been disrupted as a result of the action which is expected to last for up to six days.
Martin Skelly, President of the Irish Travel Agents Association, said the longer the strike goes on for - the more passengers and airlines will be affected.
“We commend Ryanair and Aer Lingus for their prompt actions to minimise disruption to Irish travellers, but due to the degree of disturbance the strike has created, unfortunately many flights have been cancelled and many others face extensive delays”, he said.
“All of our member travel agents are working closely with business and leisure customers in an attempt to minimise inconvenience by keeping them up to date with delays and cancellations as well as assisting them with rebooking flights and changing travel plans.”