Heathrow, Gatwick and London City airports have been among the most-impacted after a “technical issue” grounded scores of flights across the UK.

Britain’s air traffic control service, Nats, said just before 2pm it was investigating a “technical issue” which had delayed departures across most of the UK’s biggest airports.

The fault sparked travel chaos at London’s top air hubs, with as many as 240 flights having already been cancelled, according to data from flight tracking service Airnav Radar.

In an update at 3:25pm, Nats said it had identified that the issue related to its flight processing system.

In a further update at 4:40pm, Nats said it had “implemented a fix” and that its flight system was “starting to recover.”

In a statement on its website, Nats said: “We are continuing to work closely with our airline and airport customers on recovery.

“We apologise sincerely for the disruption to people’s journeys today and they should continue to check with their airline.”

Heathrow Airport said arriving flights are not affected.

In a statement the airport said: “The air traffic control service NATS is experiencing a technical issue which is impacting departing flights at UK airports.

“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.”

British Airways, which has been forced to delay the departure times for dozens of flights, said it was “currently experiencing disruption.

“This is out of our control and our teams are working hard to get your travel plans back on track as quickly as possible.”