LONDON, Mar 22: The United Kingdom's Heathrow Airport has confirmed that it is “open and fully operational” as of Saturday, March 22. The confirmation came hours after a British Airways jet touched down at the airport late Friday, nearly 18 hours after a fire at an electrical substation caused a power outage and forced the closure of the air hub.

With the airport's return to normal operations, passengers will continue to face delays and cancellations, a PA media report said. According to FlightRadar24's flight tracking service, at least 1,350 flights to and from Heathrow were affected, with disruptions expected to continue for days.

Witnesses in west London had reported hearing a massive explosion, followed by a fireball and huge plumes of smoke as the fire engulfed the electrical substation near one of the busiest airports in Europe.

The Metropolitan Police said they are not treating the incident as suspicious, adding that the London Fire Brigade's investigation is focusing on the electrical distribution equipment.

Heathrow airport chief executive Thomas Woldbye had told reporters on Friday afternoon, "We expect to be back in full operation (tomorrow), so 100 per cent as a normal day. Passengers should come to the airport as they normally would. There's no reason to come earlier."

About the power outage, which forced the airport closure, chief Woldbye said that a back-up transformer failed, which means that systems had to be shut down in accordance with safety procedures so that power supplies can be restructured from two remaining substations, enabling the air hub to get enough electricity supply.

Earlier transport secretary Heidi Alexander had said that she was in close contact with the Energy Secretary, the Home Secretary and with Heathrow to ensure "that any lessons we need to learn from the systems that the airport has in place are learned".