LONDON — Britain’s air traffic control system said it was hit by a technical issue on Monday that threatened delays and cancelations to flights in and out of the country on a busy national holiday.
“We are currently experiencing a technical issue and have applied traffic flow restrictions to maintain safety,” a spokesperson with Britain’s National Air Traffic Service told NBC News just after 12:30 p.m. local time (7:30 a.m. ET).
It said engineers were working to find and fix the fault, but it was not clear how long it would take to resolve the issue.
In the meantime, a spokesperson said air traffic personnel were having to input flight plans manually.
“This morning’s technical issue is affecting our ability to automatically process flight plans,” they said. “Until our engineers have resolved this, flight plans are being input manually which means we cannot process them at the same volume, hence we have applied traffic flow restrictions.”
“Our technical experts are looking at all possible solutions to rectify this as quickly as possible,” they said.
London’s biggest international hub, Heathrow Airport, said that “as a result of national airspace issues there is disruption to flights across the UK.”
Stansted and Gatwick Airports in London as well as Manchester Airport in the north of England said that flights were impacted by the issue.
European air traffic authority Eurocontrol warned of “very high” delays because of a “flight data processing system failure” in the U.K.
Earlier, Scottish airline Loganair said in a post on X, the social media platform formerly known as Twitter, that a “network-wide failure of UK air traffic control computer systems” had occurred early Monday.
The airline said it was hopeful it would be able to operate most intra-Scotland flights with a minimum of disruption, but said north-south and international flights could be subject to delays as a result of the issue.
The incident comes on a busy travel day for U.K. residents, with Monday a nationwide public holiday.
A number of social media users said they were stuck on planes on the tarmac. NBC News was not immediately able to verify their accounts.
One traveler who told Reuters that they were on a plane being held on the tarmac at Budapest said the pilot informed passengers that they were delayed due to a massive computer failure.
They said passengers faced a possible 8 to 12-hour delay. NBC News was not immediately able to verify that.
This is a developing story. Please check back for updates.