More than one hundred flights in and out of Irish airports have been impacted after British airspace was hit by a technical fault.
Britain's National Air Traffic Services (NATS) said it was experiencing a “technical issue”, however that has since been "identified and remedied".
NATS said earlier it was "experiencing a technical issue and have applied traffic flow restrictions to maintain safety.
“Engineers are working to find and fix the fault. We apologise for any inconvenience this may cause.”
Media Relations Manager at daa, the operator of Dublin Airport, Graeme McQueen, said their team are working hard to support all passengers and ensure those impacted by today's air traffic control issues in the UK resume their travel plans "as quickly and as safely as possible".
"Passengers intending to fly today and tomorrow are reminded to check the status of their flight with their airline, before travelling to the airport," he added.
Cork and Dublin airports have warned customers that the issue is causing both delays and cancellations.
"Air Traffic Control issues in the UK today are resulting in delays and cancellations to some flights into and out of Cork Airport," read a statement on X, formerly Twitter.
"We advise all passengers due to travel today to check the status of their flight with their airline in advance of travelling."
Dublin Airport issued a similar statement.
Ireland West Airport, also known as Knock Airport, said passengers are advised to expect delays on some flights. Shannon Airport said the forced restriction of aircraft flow has resulted in the cancellation of the outbound (FR1182) and inbound (FR1183) Ryanair Gatwick service.
A spokesperson for Shannon Airport has advised all passengers due to travel from Shannon on Monday afternoon to check the status of their flight with their airline in advance of travelling.
In Cork Airport, seven arrivals have been cancelled, and three have been delayed.
The seven cancelled arrivals include the 13.45 flight from Paris CDG, the 14.55 from Liverpool, the 15.10 from London LHR, the 16.05 from London STN, the 16.35 from Frankfurt FRA, the 16.35 from Manchester, and the 16.40 from Amsterdam.
Seven flights due to depart from Cork Airport have also been cancelled, and three departures have been delayed. The seven cancelled departures include the 12.15 flight to Liverpool, the 12.50 flight to London STN, the 13.40 flight to Manchester, the 14.25 flight to Paris CDG, the 15.15 flight to London HTR, the 17.10 flight to Amsterdam, and the 17.45 flight to Frankfurt FRA.
As of 2.15pm, 10 flights departing from Dublin Airport have been delayed and 26 flights due to depart from Dublin Airport have also been cancelled. Those include flights to various London airports, La Rochelle, Berlin, Amsterdam, Manchester, Munich, Hamburg and Budapest.
A further 42 flights due to arrive at Dublin airport have also been delayed, and a further 20 arrivals have been cancelled altogether.
They include flights from Edinburgh, Malaga, Paris, Warsaw, Krakow and various airports in London.
Minister of State for transport Jack Chambers warned of a “major” knock-on impact on flights to and from Ireland as a consequence of Britain's air traffic control fault.
“There’s traffic flow restrictions have been introduced to maintain safety in the sky and it will have significant impacts on passengers flying in and out of Dublin, and there are multiple slot restrictions,” Mr Chambers told RTÉ Radio One.
“So, we’d encourage customers to contact their airline for an update but it will have a major impact on Irish travel because, obviously, the nature and the proximity to UK space.
“There will be an impact and delays of several hours for many passengers, and we’d encourage them to contact their airlines.”
An Aer Lingus spokesperson said: “Due to a failure of the UK air traffic control flight planning systems, which is outside of Aer Lingus’ control, there are severe restrictions on all flights into the UK and flying over UK airspace today.
“We would ask you to check the status of your flight before coming to the airport today as delays and cancellations are likely.”
Ryanair said: “Due to another UK ATC failure, Ryanair will be forced to delay/cancel a number of flights to/from the UK today, Mon Aug 28.
“All affected passengers will be notified of their options to change flights (free of charge) to another Ryanair flight or receive a full refund.”
At Stansted, Ryanair passengers told PA they had been told to wait at their gate until further notice.
British Airways said in a statement: “We are working closely with NATS to understand the impact of a technical issue that is affecting UK airspace and will keep our customers up to date with the latest information.”
BBC presenter Gabby Logan said she had been caught up by the issue.
She posted on X: “On a plane on the runway at Budapest airport. After almost 3 weeks away from home I am hours from hugging my family.
“And have just been told UK airspace is shut. We could be here for 12 hours. So we sit on the plane and wait.”