Tuesday saw the 50th French strike since 2009
A number of flights between Ireland and France were cancelled Tuesday due to an air traffic control strike in France.
Ryanair says customers will be updated on their flight status via email and/or the mobile phone number provided at the time of booking.
They are being advised to also monitor their flight status online.
The carrier was also warning of further cancellations as a result.
"Unfortunately, further flight delays and cancellations are likely and customers are asked to please monitor this notice which will be updated throughout the day", it says.
"Ryanair sincerely apologises for any inconvenience caused by these unjustified ATC disruptions which are entirely outside of our control", it adds.
It is offering some customers the chance to either re-book flights, or apply for a refund.
While Aer Lingus says it had cancelled eight flights - saying those who have bookings on the cancelled flights may change for free online to another date of travel or may request a full refund.
Ryanair has launched an EU wide online petition to prevent Europe's Air Traffic Control (ATC) unions going on strike and closing skies over Europe.
It has called again on the European Commission to take action to prevent the skies over Europe being closed by French ATC union strikes, targeting the European Championships.
Ryanair says it has been forced to cancel 44 flights on Tuesday, to/from and over France, in what will be the 50th French strike since 2009, and 10th in the past 12 weeks.
In accordance with EU261 regulations, customers will not be entitled to claim for compensation as a result of the industrial action.