Flights from London airports are beginning to return to normal after Nats, the UK air traffic controller, confirmed it has restored power to systems at Swanswick control centre in Hampshire
Earlier in the day, a power outage closed London airspace and suspended flights from London airports.
Flights from Heathrow, Stansted, Gatwick, Luton and City Airport are arriving and departing, but experiencing delays and cancellations.
Manchester airport had been on standby accept some flights diverted from the capital.
Eurocontrol, Europe's airspace regulator, had originally said it was likely airspace would be closed until 7pm UK time.