Irish airline Aer Lingus has apologized to customers after it had to cancel 51 flights to and from Dublin Airport with UK or European destinations.
Footage on social media showed thousands of people queuing outside Terminal 2 on Saturday morning at the airport after digital systems failed.
The airline said its systems had now been restored and flights on Sunday were scheduled to operate as normal.
The airline said customers affected by the disruption will be able to change their travel plans free of charge.
A statement from the company said: “Aer Lingus sincerely apologizes to customers for the serious disruption caused today by the unavailability of key check-in, boarding and our website systems.
“This system outage was caused by a connection failure in services from a UK network provider.
“The outage has now been restored and we are taking steps to bring all our systems back online.
“Aer Lingus had to cancel 51 flights today, mainly to and from Dublin/European and UK destinations.”
The airline said it was operating all its transatlantic services from Dublin, albeit with delays and reduced passenger numbers in some cases due to security restrictions in place as a result of the outage.
It said transatlantic services from Shannon were operating as normal and Aer Lingus Regional (operated by Emerald Airlines) would operate with some delays.
Aer Lingus informs customers that operations are planned to function as normal tomorrow
The statement said: “Any customer affected by today’s disruption will be able to apply for a refund or change their travel plans, free of charge through Aerlingus.com, our call centers and our social media channels.
“As systems have now been restored, we are contacting customers directly to accommodate them as efficiently as possible.
“We have made additional customer service agents available to handle high call volumes – please bear with us as we attempt to service all customer enquiries.
“We will also share information about customers’ rights.
“Aer Lingus informs customers that operations tomorrow are planned to operate as normal.
“Customers are advised to arrive at the airports at the usual time for their scheduled flights.”
The technical error affected check-in, boarding and the company’s website.
This led to the airline having to cancel most flights to and from Dublin Airport to Europe and the UK after 2pm.
It also prevented the airline from communicating directly with customers, many of whom turned up at Dublin airport.
In a tweet, Dublin Airport said affected passengers should contact the airline directly about next steps.
The airport also said no other airlines are affected.
Customers reported long queues at the airport on Saturday as Aer Lingus check-in for earlier flights was handled manually.
Lisa Webb from Which? said: “Aer Lingus’ sudden cancellations of flights to and from the UK and Europe will cause thousands of passengers distress and anxiety about their travel plans.
“In incidents such as these, airlines should offer the option of refunds or rerouting passengers on any reasonable route as quickly as possible, using other airlines where necessary.
“Aer Lingus must also provide clear information to affected customers about their right to compensation.”