Hundreds of flights in and out of London's airports have been delayed or cancelled.
Eurocontrol, the organisation in charge of the safety of air navigation, explained that the problem is down to a ‘computer failure’ at the NATS UK air traffic control centre in Swanwick, Hampshire.
The delays affected London’s Heathrow and Gatwick, which then had knock on effects to other airports in the country.
Passengers stranded at the airports took to social media to complain about the disruption.
All dressed up and nowhere to go: Planes circling above Heathrow pic.twitter.com/Lu5FVTE22X— Steve Anderson (@steveanderson87) December 12, 2014
Heathrow is so unreliable— ◄ ► AYO.F (@_Ayo17) December 12, 2014
Heathrow BA terminal 1 standstill for more than three hours can we at least order delivery?!— yara j dib (@yarajalkh) December 12, 2014