London-Heathrow Airport, one of the busiest commercial flight hubs in the world, will be completely closed on Friday, following a serious fire tonight at a nearby electrical substation, resulting in a major power outage across West London, which includes Heathrow Airport. Thousands of flights and millions of passengers are expected to be affected; with over 120 flights heading to Heathrow currently in the air across the world, which will all be required to divert to other airports in the U.K. and Europe. Authorities have not yet said if they expect Heathrow to be reopened by Saturday.