From The New York Times:
Flights were diverted, passengers were stranded amid mass cancellations and thousands of expectant travelers were scrambling for alternatives as London’s Heathrow Airport was forced to close on Friday following a power outage caused by a major fire at a nearby electricity substation.
Travel chaos rippled across the globe as the airport, one of the world’s top flight hubs, ground to a halt, forcing aircraft to reroute to other European cities or turn around in midair. Heathrow officials said the airport would remain closed until 11:59 p.m. local time, but the disruptions to travel were expected to last for days as airlines struggle to rebook passengers into and out of a hub that typically handles 1,300 flights a day.