Air traffic control in London was slowly getting back to normal after an airspace shutdown caused chaos on Friday afternoon (12 December).
A radar problem at an air traffic control centre in Swanwick, Hampshire, knocked out the running of flight paths over the capital city for an hour.
It caused dozens of flights to be cancelled or delayed for hours during the afternoon, with the problem expected to last until 7pm.
But by 5pm some of the air traffic control system was returning to normal, say the company responsible for organising London airspace.
"We are in the process of returning to normal operations. We apologise for any delays and the inconvenience this may have caused," a spokesman said.
"Further information will be released as it becomes available."
However, some disruption is expected to be felt for hours ahead.
Passengers are advised to check with their airline for information.