Travel disruption could last for days after flights were cancelled leaving thousands of passengers stranded during a technical fault in the UK’s air traffic control (ATC) system.

Transport Secretary Mark Harper said it was the worst incident of its kind in “nearly a decade” and announced an “independent review” will be carried out.

The issue started on Monday after ATC provider National Air Traffic Services (Nats) suffered what it described as a “technical issue” preventing it from automatically processing flight plans.

This resulted in the number of flights being restricted while the plans were checked manually, leading more than a quarter of flights at UK airports to be cancelled.

Nats said at 3.15pm on Monday the problem was resolved, but disruption continued into Tuesday as many aircraft and crews were out of position.

At Heathrow Airport on Tuesday, at least 32 departures and 31 arrivals were cancelled.

British Airways, which operates the most flights to and from the west London airport, was the worst affected airline.

There were at least 23 departures and 51 arrivals cancelled at Gatwick on Tuesday.

Prime Minister Rishi Sunak told broadcasters: “I know people will be enormously frustrated by the disruption that’s impacting them.

“Thankfully things like this are rare and the issue itself was fixed in a matter of hours, but the disruption obviously is continuing and will last for a little while longer.

“The Transport Secretary is in constant dialogue with all the industry participants, he will be talking to airlines specifically later today and making sure that they support passengers to get home as quickly as possible.”

Transport Secretary Mark Harper told GB News: “This was a technical fault. We do not think this was a cybersecurity incident.

“And what will happen now with an incident of this magnitude is there will be an independent review.

“The Civil Aviation Authority will be putting together a report in the coming days, which obviously I will take a look at to see whether there are lessons to learn for the future, to see whether we can reduce the impact of this again.

“It’s nearly a decade since there was a significant issue like this.

“We want to make sure it doesn’t happen again, because of all the disruption that’s been caused to passengers across the country.”

Passengers wait at a departure gate at Ferenc Liszt International Airport in Budapest, Hungary, as flights to the UK and Ireland were cancelled
Passengers wait at a departure gate at Ferenc Liszt International Airport in Budapest, Hungary, as flights to the UK and Ireland were cancelled (Martin Rickett/PA)

An unprecedented ATC systems failure in December 2014 led to widespread disruption at airports.

In relation to the latest incident, Rob Bishton, interim chief executive at regulator the Civil Aviation Authority, said: “As part of our regulatory oversight of its activities, we continue to engage with Nats, and once its investigation is fully complete an incident report will be provided to the UK Civil Aviation Authority.

“The report’s outcomes will then be shared with the Secretary of State for Transport.”

Aviation analytics company Cirium said 790 departures and 785 arrivals were cancelled across all UK airports on Monday.

That was equivalent to around 27% of planned flights.

Passengers stuck in the UK and abroad described their frustration, as some had no idea when or how they would get to their destination.

Katrina Harrison and her family – including one-year-old twin grandchildren – spent the night at Leeds Bradford Airport after their flight to Antalya, Turkey was cancelled on Monday afternoon.

Ms Harrison, from Stockton-on-Tees, told the PA news agency: “There were no hotels to stay in, we couldn’t get the car out of the car park.

“We haven’t slept, we tried to sleep on the floor but couldn’t. Luckily the children could sleep in the pram.

“The holiday was supposed to be a family celebration of a few things. We’ve spent £12,000 on it and we’ve been treated like muck.”

Ryan and Kirsty Fawcett, from Selby in North Yorkshire, were at East Midlands Airport with their two-year-old twin sons for their first holiday as a family – and the couple’s first since 2019 – to Antalya in Turkey.

Their flight on Monday afternoon was cancelled, and after staying in a hotel overnight, they were booked on another departure on Tuesday morning that was also axed.

Ms Fawcett said: “What has annoyed us more is we have been told ‘just sit and wait around’, with the extra expense of hotels and things.

“What if we didn’t have money spare?”

Heathrow passenger figures
Passengers stuck in the UK and abroad described their frustration, as some had no idea when or how they would get to their destination (Jordan Pettitt/PA)

Aviation consultant John Strickland said providing ATC for flights is “complicated”.

He went on: “Systems are meant to be robust. They are pressure tested and that does give a very high level of reliability.

“But as we’ve seen in other parts of the industry, and undoubtedly in other industries too like the banking sector, there is a vulnerability in which relying on IT systems presents.”

Passengers were urged by airlines to check before they leave for the airport as their flight times may have changed.