Aer Lingus passengers were hugely critical of the airline over the weekend following the almost complete collapse of the company’s computer systems. Some of the issues were resolved and are back up and running but many passengers remain stranded overseas and having difficulty contacting support desks.

The systems failure caused 51 flights to be cancelled on Saturday and four more on Sunday, disrupting the travel plans of thousands of passengers causing huge queues and chaotic scenes at Dublin and other airports.

Aer Lingus blamed a “major break in connectivity” at its UK-based network provider for downing its cloud-based IT system. Passengers were unable to check-in online, print out boarding passes, book flights or have any electronic communication with the airline.

Aer Lingus had to revert to manual check in which again led to long delays and disruption.

The technical issues were resolved within 24 hours, but about 5,000 people are expecting compensation if the airline cannot show that they were a result of extraordinary circumstances beyond its control.

Passengers could claim that a system crash and inadequate contingency plans are the responsibility of any airline, so the “beyond its control” clause might not apply.

It is likely the decision regarding compensation will be made by the Commission for Aviation Regulation.

The aviation regulator advised passengers who wish to make a claim for expenses, refunds or compensation to contact the air carrier directly. “If you do not agree with their decision, you can refer the matter to the Commission for Aviation Regulation and we will deal with it at no cost to yourself”.

Compensation is set down in European Union regulations and amounts to €250 per passenger for all flights of 1,500km or less; €400 for all EU flights of more than 1,500km and €600 for all other flights of 1,500km-3,500km.

Passengers due to fly home from Europe on the weekend were told they could not be accommodated until the middle of this week, while Transatlantic passengers had virtually no way home.

In a statement, the airline said it “sincerely apologises to customers for the severe disruption”. It added that it had made “additional customer service agents available to deal with high call volumes” and promised to “work assiduously to reaccommodate disrupted customers as efficiently as possible”.