Air traffic control company Nats has "identified and corrected" the technical problem which caused delays to thousands of flights in the south of England.
In a statement, the company said:
Operations are now returning to normal and we are working with the airports, airlines and (Europe-wide organisation) Eurocontrol to clear the backlog of flights to ensure disruption is kept to a minimum.
Outbound delays from the UK have generally been limited to 20 minutes. We regret any inconvenience this technical problem has caused. However, our first priority will always be the safety of the flying public.