Arrivals and departures had to be cancelled from Corfu, Amsterdam, Bristol, London Gatwick, Liverpool and Manchester.
Newlyweds Taylor and Darren Galway, from Ballysillan in north Belfast, have been left devastated after missing out on their honeymoon in Corfu, Greece.
Mrs Galway told the Belfast Telegraph: “Ten minutes before boarding we had our flight to our honeymoon destination cancelled. No reason, no help, nothing at all, and now £2,000 out of pocket for a hotel we now aren’t going to be at.
“I’m absolutely heartbroken. It’s ruined. What was an amazing wedding on Sunday has now just turned into me crying, with no honeymoon, nothing at all. They didn’t offer us another flight — no alternative or even a choice to go elsewhere.
“We have to try to claim back £2,000 from our hotel through insurance. We can’t get any flight for weeks and, with me being self-employed, it’s not easy to keep closing my business.
“EasyJet, quite frankly, are a disgrace. How they are allowed to do this 10 minutes before boarding, then being escorted out of the airport...”
Belfast Telegraph journalist Niamh Campbell was also affected as she attempted to make her way to Liverpool for birthday celebrations and, as a Liverpool FC fan, to soak up the atmosphere ahead of the Champions League final on Saturday.
She had to travel to Dublin for a Ryanair flight to Liverpool in order to make it in time for a pre-booked tour of Anfield. The only other alternative was an eight-hour boat journey.
Ms Campbell said: “I’ve never seen such disorganised chaos in my life. Belfast International Airport doesn’t have an EasyJet help desk. Passengers were only told 40 minutes prior to their flights to Liverpool and Corfu that they were both cancelled and the airport staff couldn’t usher us out of the building quick enough.
“Lots of people were going to Corfu for holidays and there were stag and hen parties for Liverpool left stranded.
“We were told to just change flights for that night, as they’re free, but they were all sold out. It’s completely shambolic how EasyJet have treated people... and I honestly can’t believe it’s allowed to happen.
“Never mind the financial stress it has put on to people, but the pressure of missing events and knock-on effects such as pre-booked, non-refundable accommodation as well.
“It is beyond ridiculous. They have a lot to answer for and they will definitely have to pay compensation for all the add-on, knock-on effects this has had on people’s trips.”
Bernard Quinn explained that his family risked missing a family wedding. Three adults and two children were booked to fly with EasyJet on a 5.30pm flight from Belfast to Bristol.
Fortunately, they managed to get an EasyJet flight to Bristol last night, but only after a “bit of a panic”.
Mr Quinn added: “The downside is we have taken half-day holidays to take the earlier flight, as this flight is very late for kids travelling with us.
“However, it’s the only option that supported our need to be in Bristol for tomorrow morning.”
That option allowed them to use the same car park and hotel booking.
The latest delays follow a difficult week for EasyJet passengers, with multiple last-minute cancellations reported.
The Consumer Council has since issued advice for passengers on their rights in the event of a cancellation.
Richard Williams, head of transport at the Consumer Council for Northern Ireland, said: “If your flight is delayed, cancelled or you are denied boarding, you are entitled to assistance, including food, drink and overnight accommodation if needed.
“Passengers should keep receipts for any expenses and also keep any evidence of any contact made by EasyJet.”
He added that if the flight is cancelled, the airline must also offer the option of a refund within seven days or alternative transport to your final destination.
Mr Williams said that passengers should know they may also be entitled to compensation due to their flight being cancelled, despite EasyJet calling the IT problems “an extraordinary circumstance” in which they do not need to pay compensation.
In order to claim compensation, passengers can complete an online form on EasyJet or Tui’s website.
A statement from the airline said: “EasyJet can confirm that the earlier IT systems issues have now been rectified. Unfortunately, they resulted in some cancellations earlier [on Thursday] and while we expect to operate most of our remaining flying programme, some may still be subject to some disruption in the coming hours.
“We advise customers due to travel with us to continue to check Flight Tracker for the status of their flight before making their way to the airport. We apologise for the inconvenience caused and customers can apply for compensation in line with regulations.”