London’s Heathrow airport will be closed all day on Friday, sparking global travel chaos, after a fire at an electrical substation caused a “significant power outage” there, and left thousands of homes without power. The shutdown occurred just hours before the travel hub – one of the busiest two-runway airports in the world – was due to open, forcing at least 120 flights that were already in the air to divert, according to Flightradar24, with more than 1,300 arrivals and departures expected to be affected through the day. British Airways and Virgin Atlantic diverted flights to nearby Gatwick, which said