London airspace has been closed after a technical glitch at the National Air Traffic Control centre in Swanwick, Hampshire.
A power outage has been blamed for the problem that is affecting flights across the country, according to Sky News.
A message on the Nats website said: “Nats can confirm that a technical problem has been reported at Swanwick air traffic control centre. We apologise for any delays and our incident response team has been mobilised.
“Every possible action is being taken to assist in resolving the situation and to confirm the details. Further information will be released as it becomes available.”
In a further Tweet Nats said: “Airspace is open. We’re restricting traffic volumes in accordance with capability we currently have in our system.”
The estimated time for the problem to be resolved is 7pm tonight.
The Flight Radar website shows many aircraft circling around Heathrow.