Britain’s National Air Traffic Services (NATS) said airspace was “restricted”, while Eurocontrol in Brussels said airspace over London was briefly shut.
“We’re restricting traffic volumes in accordance with capability we currently have in our system,” NATS said in a tweet.
The problem was identified at the Swanwick air traffic control centre in southern England.
In a statement, the agency said: “UK airspace has not been closed, but airspace capacity has been restricted in order to manage the situation.”
Severe travel delays were expected because of the restrictions, with British media reporting that the malfunction was a “radar display issue”.
Eurocontrol earlier said: “All London airspace is closed due to computer failure until 1900 GMT”.