LONDON — London Heathrow Airport declared itself “fully operational” on Saturday after a major power outage caused by a fire at a nearby electrical substation shut down the UK’s busiest airport for nearly a day.

The disruption stranded over 200,000 travelers, canceled more than 1,300 flights, and triggered a nationwide debate over the vulnerability of critical infrastructure.

While airport authorities said hundreds of additional staff were working to assist stranded passengers and that an extra 10,000 seats had been added to Saturday’s schedule, the impact is expected to last for days.

Airlines, including British Airways, are still repositioning aircraft and crew. BA estimated that it would operate about 85% of its scheduled flights on Saturday.

The outage began Friday morning when an explosion and fire tore through a substation two miles from Heathrow, cutting power to the airport and over 60,000 surrounding properties.

The London Fire Brigade brought the blaze under control after seven hours, but Heathrow remained shut for nearly 18 hours.

Authorities said there was no indication of foul play, and the fire is not being treated as suspicious. However, the scale of the disruption has raised alarm across political and public circles.

Toby Harris, chair of the National Preparedness Commission, called it a "huge embarrassment for both Heathrow and the UK."

He criticized the country’s increasing dependence on lean infrastructure models, which prioritize efficiency over redundancy.

“You have to plan for things going wrong,” he said, adding that the UK has stripped away too much backup capacity in the name of cost-cutting.

Heathrow CEO Thomas Woldbye defended the airport’s response and pointed out that backup power systems were in place but were not designed to run the entire airport.

“The situation was not created at Heathrow,” he told the BBC. “The airport didn’t shut for days. We shut for hours.”

Woldbye insisted similar incidents would affect any major airport. “Heathrow uses as much electricity as a small city,” he said.

The event has prompted comparisons to previous large-scale disruptions, including the 2010 volcanic ash cloud from Iceland’s Eyjafjallajökull eruption, which grounded air traffic across Europe.

The UK government acknowledged the need for an investigation into how a single substation failure could paralyze Europe’s busiest air hub and promised to ensure such widespread disruption “does not happen again.” — Agencies