Heathrow executives are defending their response to a fire that shut down Europe's busiest air hub for almost a day. It comes after Britain's energy system operator suggested the airport had enough electricity from other sources to keep running. More than 1,300 flights were canceled Friday after a fire destroyed one of the three electrical substations that supply Heathrow. The chief executive of National Grid told the Financial Times that "each substation individually can provide enough power to Heathrow" to stay open. But Heathrow said safely restarting operations "was a significant challenge." Heathrow says it ran a full service on the weekend and expected to do so again Monday.

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 from the airport and took firefighters around seven hours to bring under control. Authorities say they found no evidence that it was suspicious. The fire affected at least 1,350 flights to and from the airport and the impact is expected to last days. After power was restored, arrivals resumed at the airport. Departures are expected to resume later Friday.