Ryanair has apologised after announcing it will cancel up to 50 flights every day until the end of October.
The company says it's because of a backlog in annual leave for staff and to improve punctuality which has fallen below 80% in the first two weeks of September.
The airline says that's because it has to allow staff to take a backlog of leave by the end of the year.
It's also blamed Air Traffic Control restrictions, and is trying to restore its punctuality record.
Ryanair says it only affects two per cent of its schedule.
Passengers are being advised that they will receive notification by email if their flight is affected.
Robin Kiely, Head of Communications with Ryanair, says "We apologise sincerely to the small number of customers affected by these cancellations, and will be doing our utmost to arrange alternative flights and/or full refunds for them".
Meanwhile, the Commission for Aviation Regulation is encouraging passengers affected by this to be aware of their rights.
In a statement, the Commission said "If you have been affected by the Ryanair programme of flight cancellations you are entitled to a choice of refund or rerouting. Compensation may also be payable depending on the notice period Ryanair has given you".