Flights around the UK are facing delays and disruption due to an air traffic control issue which has affected a string of airports including Heathrow and Gatwick and is expected to take “some time” to resolve.

About 200 flights have been cancelled and the number is expected to rise, flight monitoring website Flightradar24 said.

Departures from London airports are most severely affected, with few take-offs since a fault was reported early on Tuesday afternoon.

Airlines renewed calls for the air traffic control service provider Nats to be overhauled after the third major incident in just over three years.

Most flights due to depart Heathrow, Gatwick, Stansted and London City airports since 2pm appeared to have been delayed or are yet to take off.

About 90 flights in and out of Heathrow and Gatwick had been cancelled by 4.15pm, according to data by analytics company Cirium.

Flights from other airports around the UK, including Manchester, Edinburgh, Birmingham and Belfast airports, have also been affected.

Ryanair said more than 65,000 passengers had been delayed with 50 flights cancelled. The knock-on effects are now affecting flights around Europe, according to easyJet. Eurocontrol said some inbound flights were being held at airports abroad, with disruption likely to continue until the evening.

The air traffic control service Nats said at 1.46pm that it was “investigating a technical issue which is causing some disruption to flight departures”.

Nats later added it had identified the problem, which was in its flight processing system. It said: “Our engineers are on site and working urgently to resume normal operations as quickly as possible. We recognise the ongoing disruption to travel, for which we sincerely apologise.”

It continued: “Flights are still departing and airspace is open, but recovery will take some time. We will provide further updates as soon as possible.”

In a statement, Heathrow added: “We are supporting our local Nats team in their efforts to resolve the issue as quickly as possible. We will provide updated information when we have it.

“We apologise to those disrupted and advise passengers to check with their airline for latest flight information.”

Heathrow’s website showed several flights due to depart this afternoon have been cancelled. British Airways said it was experiencing some disruption and was in touch with its customers.

Belfast City airport warned of “some disruption” to flights after the technical issue affecting Nats.

“Due to the technical issue referenced below, there may be some disruption to flights due to arrive in and depart from Belfast City airport,” they said in a statement.”

A Birmingham airport spokesperson apologised to customers and advised them to “arrive at Birmingham airport (BHX) in line with their airline’s check-in requirements and to contact their airline directly for the latest flight information and updates.”

Edinburgh airport said it was aware of the issue which “may impact operations”.

The air traffic control problems follow an “isolated event” a year ago which caused widespread disruption, although it so far appears less severe than the full grounding of flights in August 2023, which prompted a parliamentary inquiry.

Airlines led by Ryanair have been increasingly critical of Nats after the outages.

Ryanair repeated its calls for Nats chief executive, Martin Rolfe, to resign. The airline’s chief operating officer, Neal McMahon, said: “Families travelling on holiday, people travelling for work and thousands of visitors to the UK have once again paid the price for Nats’ abhorrent failure.

He said the government should “stop making excuses for repeated Nats failures and appoint a new leader capable of running the UK ATC system”.

Wizz Air said: “A critical national infrastructure provider should not repeatedly bring the aviation system to a standstill. Nats is simply not fit for purpose in its current form.”

The transport secretary, Heidi Alexander, said: “I’m aware of a technical issue impacting flights at airports including Heathrow and Gatwick. Technicians have identified the issue and are fixing it as we speak. I know this will be frustrating for passengers and I’m sorry.”