Annoyed passengers posted on social media to say they were unable to check-in online or at various airports.
In a statement provided via MailOnline, Ryanair apologised and said the issue has been resolved and flights are back operating as normal.
"This morning we suffered a system outage which caused some short delays at airport check-in and boarding.
"The system has been restored and flights are operating as normal. We apologise for any inconvenience caused," the spokesperson said.
