Ryanair has had to cancel 26 flights to and from France tomorrow because of a French air traffic control strike.
In a statement, the airline also said the strike would affect flights overflying France.
It warned that further flight delays and cancellations should be expected.
The airline advised passengers to check the status of their flight online before departing for the airport.
It said affected passengers have been sent flight updates via email and text.
Ryanair said passengers affected by tomorrow's strike can transfer onto alternative flights by contacting the company's reservation centres.
Aer Lingus has said it has cancelled one return flight between Dublin and Paris due to tomorrow's strike.
In a statement this evening, Aer Lingus said there may be further delays to flights using French airspace.
The statement said that the level of restrictions will be assessed later today when further information is available.
The French strike was called by key unions against President Francois Hollande's proposal to cut business taxes to try and create jobs.
The country's DGAC civil aviation authority said airlines were reducing their flights into and out of Paris airports by 30% and those to and from the cities of Lyon, Marseille, Nice and Toulouse by 20%.
"Disruptions are expected throughout France," the DGAC said in a statement.
It said that unions representing air traffic controllers had asked their members to go on strike as part of a wider call for all public sector employees to stop work.
Four unions are protesting against Mr Hollande's "Responsibility Pact", which seeks to implement €30bn in cuts to payroll taxes and €50bn in spending cuts over three years to kickstart growth and revitalise the eurozone's second economy.
The cuts to payroll taxes will be in return for companies pledging to create more jobs, but some unions in France are worried that firms will shirk this duty as they will not be legally obliged to hire people.
They are also worried that the massive spending cuts outlined in the pact will negatively impact the public sector.