Flights have resumed at Heathrow Airport in London, with full service expected on Saturday, after a fire-induced power outage on Friday closed the major global travel hub and prompted investigations into electricity supply to the airport. More than 1,000 flights were canceled and disrupted and as many as 290,000 passengers had their travel plans affected on Friday after a fire at a nearby electrical substation brought Europe's busiest airport to a standstill for most of the day. The airport, which handled a record 83.9 million passengers last year, said its back-up diesel generators had "all operated as expected... but they are not designed to allow us to run a full operation." The airport's chief executive Thomas Woldbye apologized on Friday to passengers, calling the incident "as big as it gets for our airport." The significant power outage has caused concerns over a lack of proper contingency planning for power supply to the airport. Counter-terror officers from the Metropolitan Police are leading the investigation into the fire at the nearby electricity substation that has closed the airport. A Met spokesperson said its Counter Terrorism Command was leading the investigation due to "the location of the substation and the impact this incident has had on critical national infrastructure." Ofgem, Britain's energy regulator, announced it would commission a review "to understand the cause of this incident and what lessons can be learned." SHOTLIST: FILE: London, UK - Date Unknown 1. Aerial shot of city view; 2. Aerial shot of planes on parking apron; London, UK - March 21, 2025 3. Exterior of Heathrow Airport terminal; 4. Bus moving; 5. Luggage carts in front of terminal, billboard reading: Heathrow-making every journey better; FILE: London, UK - Date Unknown 6. Various of planes on parking apron; 7. Passengers arriving at airport; 8. Aerial shot of planes on parking apron. [Restrictions: No access Chinese mainland]