By Julia Kilian

London (UK) - Following the unprecedented power outage at London Heathrow , Europe's largest airport has resumed operations.

Individual aircraft had already taxied back to the runways on Friday evening. Airport boss Thomas Woldbye said that they expected to be "fully operational again" on Saturday morning.

The national airline British Airways, meanwhile, expects to operate around 85 percent of its scheduled flights today. However, further delays are to be expected until the situation has normalized.

It is still unclear why the fire, which paralyzed the airport for hours, broke out. Transport Minister Heidi Alexander said that there were currently no signs of sabotage. Police anti-terrorism investigators were nevertheless looking into the matter because the fire raged near a "critical part of the national infrastructure".

The airport's CEO emphasized that it was an incident with significant repercussions. "It's not a small fire," said the airport boss. The power outage was comparable to that of a medium-sized city. The backup systems, which are supposed to ensure emergency landings and evacuations, for example, had worked as intended. However, they were "not designed to operate the entire airport", said Woldbye.

The extent of the impact is not yet clear. More than 200,000 passengers were affected, according to the British news agency PA. The costs for the airport and the airlines are in the tens of millions, an expert told Sky News. In Germany , around 9,000 passengers were expected to be affected and unable to fly due to the power failure at Heathrow.

The problem: the outage at the world's fifth-largest airport by passenger volume, according to Sky, had a knock-on effect - passengers and flight crews were affected worldwide. Many people reported in the media what it was like to be stranded in the distance or to be on a plane that had to turn around on the way to Heathrow.

On Friday evening, British Airways announced the departure of an initial eight planes to far-flung destinations in Africa and Asia. The first plane to land is said to have come from London's Gatwick Airport. The airport in the south of the metropolis was one of the alternative airports for diverted flights. It takes about an hour by car to get from one airport to the other.

The fire department was alerted on Friday night and around 70 firefighters contained the fire in the substation.

"We have three of these substations, and each of them has a backup transformer," which was also affected in this case, said Woldbye. "So we weren't completely without power, but we had to reorganize our power supply." The systems were shut down for this. "This is a safety procedure that we will not circumvent," said the airport boss.

Investigating an incident of this severity takes time, said Woldbye. Everything would be "carefully analyzed". Prime Minister Keir Starmer wrote on the X platform that he would be kept regularly informed. "Thank you to our emergency services for keeping people safe," Starmer wrote.