Aer Lingus has been hit by an outage across its app and website.
Customers are being asked to allow extra time for check-in, and to check airport websites for flight status information.
The Irish airline has apologised to customers, and said flights have so far gone as scheduled.
"All Aer Lingus flights are operating as normal today," the carrier said.
"The Aer Lingus website, mobile app and self-service kiosks are now fully available for customers to check-in and manage their bookings".
However several customers have said they are still not able to access their bookings.
"When I try and log in it keeps telling me that my credentials have expired," one Twitter user said.
Another said they could login but could not access their booking.
In a statement to Newstalk, Aer Lingus said all flights were operating as normal today.
"The Aer Lingus website, mobile app and self-service kiosks are now fully available for customers to check-in and manage their bookings, following a temporary issue earlier today."
