Travel Disruptions Linger as Flights Resume at London’s Heathrow

London Heathrow Airport surged back to life on Saturday, one day after a fire at a power substation shut the travel hub down for about 16 hours, disrupting global travel and raising questions about the reliability of the British electrical grid.

The police were still investigating what had caused the fire at the substation in western London. The blaze caused a power cut to tens of thousands of nearby homes as well as to Heathrow, one of the world’s busiest airports. The Metropolitan Police in London said that there was no immediate indication of foul play, and intelligence officials in Europe and the United States said that they had no reason to think that any terrorist group or country had been involved.

Thomas Woldbye, the Heathrow C.E.O., on Saturday praised the response by emergency responders and engineering officials that allowed the sprawling airport to resume operations Friday evening.

“I’m proud of what the people did to get us out of the situation,” Mr. Woldbye told the BBC on Saturday morning. “Don’t forget, the situation was not created at Heathrow Airport. It was created outside the airport, and we had to deal with the consequences.”

Mr. Woldbye declined to comment when asked whether he should resign over the incident, which stranded thousands of travelers at other European airports, many of whom were still struggling to rebook flights over the weekend. He pledged to “look at what we can do better” but rejected criticism that the airport should have had backup systems that would have kept the power on after the fire.

“I’m sure there will be questions, but I don’t know of an airport that has backup supply that can switch on in minutes to the magnitude of what we experienced yesterday,” he said. “This same would happen in other airports.”

A Heathrow representative said on Saturday that the airport had hundreds of additional employees on duty and had added flights to the day’s schedule to accommodate 10,000 extra passengers. An average of 229,000 people a day traveled through the airport last year.

More than a thousand flights were diverted, wreaking havoc on the plans of more than a quarter-million travelers, Cirium, an aviation data company, estimated. Planes from all over the world were heading to Heathrow early Saturday, including from Brazil, Hong Kong and South Africa, according to Flightradar24, a tracking website.

British Airways, Heathrow’s largest carrier, said late Friday that it expected about 85 percent of its nearly 600 departures and arrivals scheduled for Saturday to go ahead but that delays were likely to affect all passengers. The airline said that it was also canceling flights on high-frequency routes where passengers had more rebooking options.

At Heathrow’s Terminal 3 — where Friday’s power blackout had left ticket counters dimmed and gates empty — travelers arrived early Saturday morning once trains and other transport routes to the airport had reopened.

Nicu and Sylvia Popa, who live in Crewe, in northwestern England, spent the night at a nearby hotel after their flight to Los Angeles was canceled. Mr. Popa said that he woke up several times to check for messages from the airline, Virgin Atlantic, but received nothing. By 7 a.m., flights were fully booked and the first departure they could get was for Sunday morning.

“At least they could have said come to the airport at midnight,” Ms. Popa said. “I know they don’t want to create chaos but they should have some consideration.”

The couple had spent a year planning a road trip around the U.S. West Coast. As they dealt with the delays, they found some levity in their repeated bad luck: On a previous trip in 2010, their flight from Romania to England was grounded by an ash cloud over Europe caused by a volcanic eruption in Iceland.

On Friday, the delays at Heathrow were caused by what the London Fire Brigade said was a large blaze at the substation fueled by thousands of gallons of cooling oil. The National Grid, a utility company, said that the substation’s network had been reconfigured to partly restore power temporarily to the airport and to other customers.

The fire and Heathrow’s shutdown raised broader questions about Britain’s infrastructure. Ed Miliband, Britain’s energy secretary, promised on Friday that officials would examine what had gone wrong.

“Obviously, with any incident like this, you will want to understand why it happened and what, if any, lessons it has for our infrastructure,” he told Sky News.

The biggest disruption was felt by British Airways, which operates about half the flights in and out of Heathrow each day. Sean Doyle, the airline’s chief executive, warned on Friday that the airport’s closure would have a “huge impact” for days.

On Friday, fewer than 10 of the day’s 670 flights from Heathrow took off to their scheduled destinations, departing after the airport reopened Friday evening. The airline added staff and extended the opening hours of its customer service phone lines to help stranded travelers. It encouraged passengers to check online for updates and said that it would automatically rebook people with canceled flights.

Even flights going ahead would still face delays, the airline said, and it was offering free rebooking for anyone who planned to travel over the weekend.

The airline needs to get thousands of customers to their destinations but also must find crews to take over from staff members who cannot keep working because of restrictions on how many hours they can work without time off.

On Friday, shares in IAG, the parent company of British Airways, dropped nearly 2 percent as investors considered the financial fallout from Heathrow’s closure, including the costs of providing extra accommodation to staff and customers, and how much it might have to shell out in compensation.

John Yoon contributed reporting.