Readers like you keep news free for everyone.

More than 5,000 readers have already pitched in to keep free access to The Journal.

For the price of one cup of coffee each week you can help keep paywalls away.

Support us today
Not now
Thursday 30 November 2023 Dublin: 3°C
Sasko Lazarov/ Passengers checking the departures board at Dublin Airport today following a UK air traffic control technical glitch yesterday.

UK air traffic services says fault was caused by flight data it received

There are no indications that the failure was caused by a cyber-attack, according to the UK’s National Air Traffic Services (Nats).

THE UK’S NATIONAL Air Traffic Service (NATS) has said that the air traffic control failure it experienced yesterday was caused by flight data it received, with both primary and back-up systems responding by suspending automatic processing, chief executive Martin Rolfe said.

Thousands of holidaymakers had their flights delayed or cancelled yesterday after the technical fault meant flight plans had to be input manually by controllers

The fault was remedied at around 3.15pm yesterday afternoon, but the impact on airlines was still being felt today. 

Analysis of flight data websites by the PA news agency shows at least 281 flights – including departures and arrivals – were cancelled today at the UK’s six busiest airports.

In a statement this evening, Rolfe said: “Very occasionally technical issues occur that are complex and take longer to resolve. In the event of such an issue our systems are designed to isolate the problem and prioritise continued safe air traffic control.

“This is what happened yesterday. At no point was UK airspace closed but the number of flights was significantly reduced.”

He said an initial investigation into the problem show it relates to some of the flight data NATS received.

The company’s primary and back-up systems responded to the data by “suspending automatic processing to ensure that no incorrect safety-related information could be presented to an air traffic controller or impact the rest of the air traffic system”.

Rolfe said there are no indications that the fault was a cyber-attack. 

“We have well established procedures, overseen by the CAA, to investigate incidents. We are already working closely with them to provide a preliminary report to the Secretary of State for Transport on Monday.”

He said the conclusions of the report will be made public and apologised for the fault.

“I would like to reassure everyone that since yesterday afternoon all of our systems have been running normally to support airline and airport operations as they recover from this incident.”


Earlier today, Ryanair boss Michael O’Leary slammed NATS for the “unacceptable” disruption caused over the past two days following a technical fault.

In a video message today, O’Leary described yesterday as “a very difficult day” with 250 flights cancelled, while a further 70 flights were axed today.

Speaking from the airline’s operations centre at Dublin Airport, he said: “I’m sad to report that we had to cancel about 250 flights affecting the flights of about 40,000 passengers because of long delays to flight plans, crews running out of hours.

“Last night we had 20 aircraft that couldn’t get back to their home bases so they’re out of place for today.

“Today, unfortunately, it looks like we’re going to cancel about another 70 flights.

“That’s a very small number out of the 3,200 flights we’re planning but that doesn’t mean we’re not doing everything we possibly can to try to minimise the disruption for our passengers and their families.”

The Ryanair boss said the airline had been in contact with NATS about the issue.

“We still haven’t had an explanation from them (about) what exactly caused this failure yesterday and where were their back-up systems,” he said.

It’s not acceptable that UK NATS simply allow their computer systems to be taken down and everybody’s flights get cancelled.

He added: “We hope by the end of today, Tuesday, that from tomorrow we’ll be running a normal operation.”

In a statement this morning, Kevin Cullinane, group head of communications at daa, the operator of Dublin and Cork airports, said further flights were impacted by delays or cancellations today.

“The teams at Dublin and Cork airports are working hard to support our airline partners and to ensure passengers impacted by UK air traffic control issues resume their travel plans as quickly and as safely as possible,” he said.

Passengers intending to fly from Dublin Airport today are advised to check the status of their flight with their airline before travelling to the airport, while passengers needing to re-book flights have been encouraged to do so through their airline’s app or website.

Dublin Airport has waived any car parking fees for customers returning to the airport as a result of delays.

A spokesperson for Aer Lingus stated today that it continues to face “unavoidable cancellations and delays”.

“We are doing everything possible to minimise any further disruption to our customers and we apologise to all those impacted for the inconvenience caused, which is due to circumstances outside of our control.”

Aviation analytics company Cirium said across all UK airports yesterday, 790 departures and 785 arrivals were cancelled. That was equivalent to around 27% of planned flights.


There is speculation the fault was caused by a French airline submitting a flight plan to NATS in the wrong format.

NATS would not comment on whether that was accurate.

Former NATS controller Doug Maclean said he did not know whether the actions of a French carrier were to blame, but believed an “operational glitch” was likely to have happened.

Asked if the problem could reoccur, he replied: “I wouldn’t think that there’s much likelihood of a failure but as long as NATS don’t say anything it’s a perfectly legitimate question.”

He added: “What was the problem? I don’t understand why they’re so closed mouth about it.”

Downing Street did not rule out the possibility that an inputting error by a French airline could have caused the disruption.

29082023-dublin-ireland-photo-sasko-lazarov-rollingnews-ie Sasko Lazarov / Passengers at Dublin Airport today were facing long delays as a technical glitch in the UK yesterday meant flight plans had to be input manually by controllers. Sasko Lazarov / /

The British Prime Minister’s official spokesman said: “There’s going to be, think you’ll know that there’s going to be an investigation by the CAA (Civil Aviation Authority), and a report shared with Government.

“I think (Transport Secretary) Mark Harper confirmed this morning he’ll be getting that in days.

“I’m not going to pre-empt that. I’ve seen, obviously, various bits of speculation, but I’m not going to pre-empt the work that needs to be done.”

But he added that experts had confirmed it was a “technical issue, not a cyber security incident”.

Asked if officials would speak to counterparts across the English Channel, the spokesman said “you would expect them to be speaking regularly” with other countries, “but I’m not aware of any specific conversations with French counterparts”.

With reporting from Hayley Halpin, Jane Moore and Press Association

Your Voice
Readers Comments
This is YOUR comments community. Stay civil, stay constructive, stay on topic. Please familiarise yourself with our comments policy here before taking part.
Leave a Comment
    Submit a report
    Please help us understand how this comment violates our community guidelines.
    Thank you for the feedback
    Your feedback has been sent to our team for review.

    Leave a commentcancel