Dublin Airport has advised passengers of further disruption affecting check-in and boarding systems at Terminal 2.
It marks the third day of disruption to the airport's check-in and baggage drop in Terminal 2 following Saturday's cyber attack which impacted several airports across Europe.
Airport operator daa said it is continuing to support airlines as they deal with the ongoing disruption.
"The Dublin Airport team is continuing to support airlines today as they manage ongoing disruption from a technical issue that is affecting check-in and boarding systems at several airports in Europe," it said.
Read more: Dublin Airport T2 disruption continues as Aer Lingus 'significantly impacted'
The operator said some airlines are continuing to use manual workarounds to issue bag tags and boarding passes in Terminal 2.
"As a result, check-in and bag drop may take longer than usual. Airlines in Terminal 1 are operating as normal," daa said.
Passengers are being advised to arrive at the airport as normal today, two hours before a short-haul flight and three hours before a long-haul flight.
"However, if you need to check in or drop bags in Terminal 2, please allow extra time," daa said.
"Passengers should contact their airline directly for the latest updates on their flight."
In a statement, Aer Lingus said its scheduled flights are planned to operate as normal today but added there may be some disruption to journeys.
"We are deploying additional staff at our check-in to assist customers and help minimise delays and ask our customers travelling from Dublin today to check-in online or via our app where possible and proceed straight to the gate with 10kg baggage, where it will be checked in at no charge.
"We will continue to update our information to passengers and are advising customers to check their SMS and our website for the latest updates. We appreciate the patience and cooperation of our customers as we continue to manage this unfortunate disruption,'’ the airline added.
The disruption is the latest in a string of hacks targeting governments and companies across the world, hitting sectors from healthcare and defence to retail and autos.
A recent breach at luxury car manufacturer, Jaguar Land Rover, brought its production to a halt.
The problems were centred on MUSE software made by Collins Aerospace, which provides systems for several airlines at airports globally, airports said.
Head of Media Relations Manager with daa Graeme McQueen said that the disruption is confined at this point to Terminal 2.
"It's not ideal, obviously, but it is having a very minimal impact.
"There are some manual processes in place, so the manual printing of boarding passes and check-in is a bit more complicated in Terminal 2, but we're getting by, but we're hopeful of a fix today so that we can get back fully to normal."
Speaking on RTÉ's Morning Ireland, he said that there are no cancellations at the moment and there are no cancellations expected.
"But I wouldn't rule it out completely because we saw what happened over the weekend," he added.
Mr McQueen said there are IT experts being flown into Dublin Airport and the other impacted airports to help fix the issue.
"It is quite complicated. It involves the rebuilding of servers and things like that. So, it is going to take time.
"We need to do a lot of testing to make sure it's ready fully to get back up when the time comes. We're hopeful of positive news today and we're hopeful that this will be the last day of disruption but there is a bit of wait and see with this over the course of the day."
Mr McQueen said that the cyber attack impacted airline systems, and explained how individual airlines have ttheir own systems to test manual processes.
"So, we've been working hard to support the airlines. I think they had to rally round and put in place these manual processes.
"But at Dublin Airport, our airlines are pretty good at that. They test it all the time. Ryanair, for example, would do manual testing on one flight every week. Aer Lingus, very similar.
"They test and they plan for these situations, and those contingency plans kick in.
"So, it hasn't been ideal. There have been some flaws. It's been tricky for some passengers, but we're getting by, and I think I would be confident to see that disruption has been minimised."
Disruption continues at Heathrow
Meanwhile, passengers at Heathrow could face another day of disruption after a cyber attack affected several major European airports.
Terror law watchdog Jonathan Hall KC said it was possible state-sponsored hackers could be behind the attack on Collins Aerospace, which operates check-in and boarding systems.
This morning Heathrow said work was continuing to "resolve and recover" from the "outage" in the system.
Mr Hall, the independent reviewer of terrorism legislation, said attributing the attack would not be easy.
Asked if a state like Russia could have been responsible for the attack, he told Times Radio "anything is possible".
He said: "Yes, it's possible that this is carried out directly by a state, but it’s equally possible to be carried out by a private entity that is, sort of, allowed to operate and does it for a combination of public and private reasons."
That meant attacks were "deniable" for states, even if hackers were based there.
He said: "There are some very capable private entities, let’s say, in Russia or China, who won’t necessarily be being directed by Russia or China.
"So it’s not as if a member of the GRU (the Russian military intelligence agency) is necessarily going into a company and saying that 'you’ve got the capability of knocking out some UK infrastructure, please go and do it now’.
"It’s also possible, in this ecosystem that exists in some of these countries, that a company, an entity, carries out a hack and simply does it for patriotic reasons, or does it because they want to curry favour, or maybe there’s some sort of informal relationship with them.
"So although we think, understandably, about states deciding to do things it is also possible for very, very powerful and sophisticated private entities to do things as well."
