Disruption to flights is expected to continue into Wednesday after a technical failure with air traffic control plunged UK airports into chaos.

Heathrow and Gatwick were hardest hit by the issue on Tuesday afternoon which led to the cancellation of more than 875 flights across the UK.

Almost 400 flights to and from the London airports were cancelled with a further 750 delayed, according to flight tracker Flightradar.

Stansted, London City and Luton airports were also affected with scores of delays and cancellations.

National Air Traffic Services (NATS) , which provides air traffic control services to 15 UK airports, said in a statement on Tuesday evening that recovery had “taken longer than we had hoped” after a technical issue in its “flight processing system” which was causing the disruption.

At about 7.30pm, Nats announced the “system issue” had been resolved.

“We are operating normally and working as hard as possible to clear the backlog of flights,” a statement on X said.

The exact cause of the fault that led to the disruption is currently not known and it is unclear how long the disruption will last.

But it is expected to take hours to clear the backlog of flights with further knock-on disruption into at least Wednesday.

Real-time flight tracking website Flightradar has said delays and cancellations will be expected tomorrow.

Meanwhile, Heathrow Airport says arrivals have been suspended for the remainder of the day "to ensure the safety of our passengers and colleagues".

A Heathrow spokesperson said on Tuesday night: "Due to the earlier technical issue affecting NATS, arrivals into Heathrow have been suspended for the rest of the day to ensure the safety of our passengers and colleagues.

“Departures have resumed, but disruption is expected to continue, so we advise passengers to check with their airline for the latest flight information before travelling to the airport. We apologise to those affected and are supporting our local NATS team and airline partners as they work through the resulting disruption."

Passengers reported waiting for hours to disembark from aircraft stuck on the tarmac, while others could be seen standing around anxiously checking noticeboards for updates on their flights, while others queued for taxis.

Josie Donoghue, who had to get off her flight from Gatwick to Ireland after spending three hours on the runway, said that getting through the London airport was like “trying to get out of Alcatraz”.

“We were trapped in there. We were told we couldn’t get out until the flights were cancelled, and then eventually they allowed us to get out,” she said.

The health worker added: “It’s just an absolute nightmare down there, it’s the only word I can use to describe it.”

Ryanair said more than 65,000 of its passengers had been disrupted and it had cancelled more than 50 scheduled flights.

Meanwhile, British Airways (BA) said it was forced to cancel or divert more than 100 flights on Tuesday which had impacted “tens of thousands of customers”.

A spokesperson for company said that despite being informed by Nats that the issue had been resolved, the “severity” of the problem means there will be a “significant knock-on impact for customers and colleagues.”

Ian Petchenik, Director of Comnunications at FlightRadar told The Standard that Heathrow and Gatwick had been most affected by the disruption.

“Heathrow and Gatwick have been most affected, especially due to the large number of out of position aircraft,” he said.

“As airlines work to move their aircraft back into position, we expect to see continuing delays and some cancellations into tomorrow.”

The incident was “entirely out of our control and incredibly frustrating for our customers and colleagues” the spokesperson added.

Budget airline EasyJet said some of its flights were “unable to operate” following the issue which was causing delays to flights across Europe.

In a post on X, Transport Secretary Heidi Alexander said she was “seeking assurances that lessons will be learned and systems that support aviation are up to the job” following the disruption.

She said she gave her “huge thanks” for those working to “get people moving”.

Passengers stranded at Heathrow and Gatwick told of their “panic” upon hearing of the delays.

Katherina Wilken and her partner were due to be flying back from Heathrow to Dusseldorf in Germany on Tuesday afternoon.

The 26-year-old said she started to “panic” when at 3pm she had no gate information for her flight which was scheduled for 2.45pm.

The couple are now due to depart Heathrow at around 7am on Wednesday.

She said: “It’s way too stressful to stay in a hotel miles away, we will probably stay here (at the airport) tonight.”

The 29-year-old told PA that Wizz Air’s next flight to Tel Aviv isn’t until Saturday.

“I’m just trying not to panic,” she added. “I’m trying to figure out what to do and find a solution. There’s always a way, so it’s fine.”

It comes after last July, a “radar-related issue” caused an air traffic control failure that grounded flights across the UK, disrupting thousands of passengers and forcing the cancellation of more than 160 flights.

The problem happened at Nats’ control centre in Swanwick, Hampshire, and affected the vast majority of England and Wales.

At the time, a Government source said the failure lasted around 20 minutes, and the level of disruption was similar to a day with bad weather.

In August 2023, more than 700,000 passengers experienced disruption when flights were grounded at UK airports when Nats suffered a technical glitch while processing a flight plan.

A Heathrow spokesperson previously said: “The air traffic control service NATS is experiencing a technical issue which is impacting arriving and departing flights across UK airports. We are supporting our local NATS team in their efforts to resolve the issue as quickly as possible. We apologise to those affected by the disruption and advise passengers to check with their airline for the latest flight information and only travel to the airport if their flight is confirmed.”