The carrier is to cancel up to 50 flights a day for six weeks
Irish airline Ryanair has published a list of cancelled flights, after it announced it is to cancel up to 50 flights a day for the next six weeks.
It says this is due to several factors, including a backlog of holiday leave to pilots and cabin crew.
The company says it is moving its holiday year from the current system of April to March to a calendar year of January to December from January 2018.
It says the backlog of crew leave must be allocated before December 31st this year to switch to a calendar leave year.
Affected customers will be contacted directly and offered alternative flights or full refunds.
Ryanair says this is required by the Irish Aviation Authority (IAA).
The airline has published a list of cancelled services here
Ryanair's Kenny Jacobs said: "Flights are operating as scheduled unless an e-mail confirming a cancellation has been received.
"We advise customers to check the e-mail address used to make their booking.
"Cancellation notices for flights cancelled up to and including Wednesday September 20th have been sent to affected customers and we will continue to send regular updates and post flight information on our website.
"We apologise to all affected customers for these cancellations. We have messed up in the planning of pilot holidays and we're working hard to fix that."
The Irish Travel Agents Association (ITAA) has expressed "strong concern" over the cancellation of flights, saying they will cause "severe problems for thousands of travellers travelling to and from Ireland."
And the Commission for Aviation Regulation says it wants all passengers affected to be aware of their rights.
"Passengers who remain unclear about their entitlements as set out in EC Regulation 261/ 2004, or who have further queries in relation to same, should contact this office at email@example.com or on 1890-787-787 or + 353-1-6611700", it says.
More information is available here