Hundreds of additional employees were on duty, and flights were added to the schedule to accommodate thousands of extra passengers, the airport said.
Heathrow Airport in London 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 flights worldwide and raising questions about the reliability of the British electrical grid.
The police were still investigating how the fire at the substation in western London started. 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 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.
But the episode triggered an immediate outpouring of frustration from affected travelers and from British politicians, who accused authorities of not being prepared enough to confront a power failure of Friday’s magnitude.
Toby Harris, a Labour lawmaker who is chairman of the National Preparedness Commission, called the closure of the airport an “enormous failure.” He told the BBC that “it sounds to me like Heathrow Airport was simply not as prepared as it should have been.”
Thomas Woldbye, the Heathrow C.E.O., on Saturday defended the response, praising emergency workers and engineering officials that allowed the sprawling airport to resume operations Friday evening.