A fire at an electrical substation knocked out power to Heathrow Airport for most of Friday, forcing Europe's busiest hub to shut down for roughly 18 hours, causing widespread cancellations and rerouting headaches, and stranding roughly 200,000 passengers. The blaze started just before midnight on Thursday at a substation about 2 miles (3.2 kilometers) from the airport and took firefighters around seven hours to bring under control. Authorities said they found no evidence that it was suspicious, and the London Fire Brigade said its investigation would focus on the electrical distribution equipment at the substation. The fire knocked out power to Heathrow and thousands of homes in the area. It affected at least 1,350 flights to and from the airport, according to flight tracking service FlightRadar 24, and the impact was expected to last several days, as passengers try to reschedule their trips and airlines work to reposition their planes and crews. After power was restored, a British Airways jet touched down just before sunset on Friday after Heathrow lifted its closure order. Further arrivals followed, including a short flight from Manchester in northwest England. A British Airways flight to Riyadh, Saudi Arabia departed from Heathrow just before 9 p.m. (2100GMT). British Airways says it will run eight long-haul flights on Friday night. The airport plans to operate full schedule on Saturday. Residents in west London described hearing a large explosion, followed by a fireball and clouds of smoke, when the blaze ripped through the substation. About 120 flights were in the air when the closure was announced. Some turned around and others were diverted to Gatwick Airport outside London, Charles de Gaulle Airport near Paris or Ireland’s Shannon Airport, tracking services showed. Lawrence Hayes was most of the way to London from New York when Virgin Atlantic announced the plane was being diverted to Glasgow.