London’s Heathrow Airport is expected to be completely up and running again by Saturday morning following a massive fire that knocked out power at the busy travel hub, the airport’s CEO said Friday.

“Tomorrow morning we expect to be back in full operation, so 100% operation, as a normal day,” Heathrow Airport CEO Thomas Woldbye said at a press conference Friday evening local time.

Passengers flying out of the airport Saturday should plan on arriving at the time they normally would, Woldbye said, while apologizing for the “unprecedented” travel headache.

Flight disruptions had been expected to drag on with long-lasting delays for days even as the airport said Friday it had “restarted” some flights to relocate planes after the blaze broke out. 

On Friday afternoon, the airport said it was “now safely able to restart flights, prioritizing repatriation and relocation of aircraft” after more than 1,350 flights were canceled or diverted from the bustling transit center.

The chaos will likely persist at least through midnight Friday as airlines scramble to move stranded planes and flight crews back into correct positions and work to help travelers whose flights were canceled, sources said.

As Europe’s busiest transportation hub, the airport is powered by a single substation that “uses as much energy as a small city” with no “full operation” backup, the airport said in a statement.

“We have back-up diesel generators and uninterruptible power supplies in place, and they all operated as expected,” the airport said. But “Heathrow uses as much energy as a small city, therefore it’s not possible to have back-up for all of the energy we need to run our operation safely.”

Five of the eight flights scheduled to leave Kennedy International Airport for Heathrow on Friday were canceled as of 11 a.m., The New York Times reported, citing departure boards at Kennedy. All eight arriving flights from Heathrow were canceled.

The blaze was still partly burning as of 3:30 p.m. local time Friday, London fire officials said. 

“Approximately 5% remains alight in isolated hotspots, and we will maintain a presence at the site until the incident is resolved,” said a statement from the London Fire Brigade. 

Sean Doyle, the CEO of British Airways, called the travel nightmare an “unprecedented situation” and said all hands are on deck to “to help us to manage as many customers as possible.”

The outage “will have a substantial impact on our airline and customers for many days to come,” he said Friday.

“Even if things do get back and running soon, we will have the logistical issue of getting new crews out to operate [rerouted] to aircraft.”

British Airways later said it had been given clearance by the airport to depart “eight of our long haul flights from Heathrow at 7 p.m. Friday.”

Only passengers on flights headed to six cities including Cape Town, Singapore and Buenos Aires should head to the airport after 5 p.m. local time, the airline said.

More than 200,000 travelers were previously advised to completely avoid the airport — which 83.9 million passengers used last year — through at least midnight Friday after the blaze knocked out power at a major substation. An average of 1,300 flights pass through the airport each day.

Counterterrorism police were meanwhile investigating the fire as of Friday morning, but no foul play was suspected, British police said. 

London’s mayor, Sadiq Khan, told Sky News that a counterterrorism probe is “not unusual” in cases of a major fire cutting off power at an airport. “There is no reason at all for anyone to be concerned or alarmed in relation to the fire at the substation,” he said.