Passengers have been advised to check the latest flight information with their airlines.
Recovery from disruptions to flights leaving the UK caused by an air traffic control issue will “take some time”, Nats has said.
Birmingham Airport said the issue was affecting airspace in the south of the UK and was “impacting a significant number of departing flights across the country”.
Heathrow Airport, the UK’s largest airport in west London, confirmed it was among those impacted but said arriving flights were “currently not affected” in a statement on Tuesday afternoon.
Manchester Airport Group, the company that operates Manchester Airport, Stansted Airport in Essex and East Midlands Airport in Leicestershire, said flights from all three had been affected by the issue.
Jersey Airport in the Channel Islands, Aberdeen, Glasgow, Southampton and Belfast airports said they were also experiencing some disruption.
Passengers have been advised to check the latest flight information with their airlines.
Nats, which provides air traffic control services to 15 UK airports, said in a statement it was “investigating a technical issue” causing disruption to some flight departures, and later said it had identified the problem was in its “flight processing system”.
The company 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.
“Flights are still departing and airspace is open, but recovery will take some time. We will provide further updates as soon as possible.
“Passengers should check the status of their flight with their airline.”
A Heathrow spokesperson said: “The air traffic control service Nats is experiencing a technical issue which is impacting departing flights at UK airports.
“Arriving flights are not currently impacted.
“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.”
The airport apologised to impacted customers.
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.
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.
