NATS has explained that its Swanwick control centre experienced a technical problem in the early hours of Saturday morning.
It said in a statement: “At night, when it’s quiet, we can combine sectors of airspace. When it gets busy in the daytime we split the sectors out again. The voice communications system is configured to enable this to happen.”
It said the glitch on Saturday morning meant it had not been possible to reconfigure the voice communications system to split out the sectors for the daytime traffic in some areas of the UK airspace.
NATS added: “Engineers are working to rectify the problem as soon as possible but this is resulting in some delays. Safety has not been compromised at any time, and we sincerely apologise for any inconvenience being caused to passengers.”