LONDON, March 23, (AP): The British government on Saturday ordered an investigation into the country's "energy resilience” after an electrical substation fire shut Heathrow Airport for almost a day and raised concerns about the UK's ability to withstand disasters or attacks on critical infrastructure. While Heathrow Airport said it was now "fully operational,” thousands of passengers remained stuck, and airlines warned that severe disruption will last for days as they scramble to relocate planes and crews and get travelers to their destinations.

Inconvenienced passengers, angry airlines and concerned politicians all want answers about how one seemingly accidental fire could shut down Europe’s busiest air hub. "This is a huge embarrassment for Heathrow airport. It’s a huge embarrassment for the country that a fire in one electricity substation can have such a devastating effect," said Toby Harris, a Labour Party politician who heads the National Preparedness Commission, a group that campaigns to improve resilience.

Energy Secretary Ed Miliband said he'd asked the National Energy System Operator, which oversees UK gas and electricity networks, to "urgently investigate" the fire, "to understand any wider lessons to be learned on energy resilience for critical national infrastructure." It is expected to report initial findings within six weeks.

"The government is determined to do everything it can to prevent a repeat of what happened at Heathrow," Miliband said. Heathrow announced its own review, to be led by former transport secretary Ruth Kelly, a member of the airport's board. Heathrow Chairman Paul Deighton said Kelly will look at "the robustness and execution of Heathrow’s crisis management plans, the airport’s response during the incident and how the airport recovered.” More than 1,300 flights were canceled and some 200,000 people stranded Friday after an overnight fire at a substation 2 miles (3.2 kilometers) away cut power to Heathrow, and to more than 60,000 properties.