Heathrow Airport has been closed until at least midnight tonight after experiencing a major power outage following a fire at a west London electrical substation.Passengers were asked not to travel to the airport "under any circumstances",

At least 1,350 flights to and from Heathrow were affected already, including several from US cities that were canceled, flight tracking service FlightRadar 24 said.

The London airport, which is one of the world’s busiest for international travel, said it expects “significant disruption over the coming days” and warned passengers not to come until it reopens.