Planes from Heathrow serve around 80 countries, and around 1350 flights had been due to land or take off from the airport’s five terminals on Friday, according to the Flightradar24 tracking website.
Around 230,000 passengers use Heathrow every day – 83 million a year – making it one of the world’s busiest airports.
London’s Metropolitan Police said the force’s Counter Terrorism Command was leading the investigation into the fire given the “impact this incident has had on critical national infrastructure”.
“While there is currently no indication of foul play we retain an open mind at this time,” a spokesman added.
Firefighters were called to the “highly visible” blaze at the substation shortly after 11.20pm local time on Thursday and around 70 were sent to battle the fire, which was later brought under control.
The outage left 100,000 homes without power overnight. Electricity distribution network National Grid said that at around 2pm GMT power had been partially restored to Heathrow as well as to local residents affected.
UK Energy Secretary Ed Miliband promised that the Government would do all it could to restore power to Heathrow quickly, as questions were raised about the airport’s “resilience”.
Frustrated passengers: ‘I’ve spent so much money'
The airport shutdown left many frustrated passengers struggling to make alternative arrangements.
“I had planned this journey three months ago ... I’ve spent so much money on tickets and everything,” said Muhammad Khalil, 28, who was booked on a flight to Pakistan to be reunited with his wife after five months.
“You can’t imagine how stressful it is for me,” he told AFP.
British Airways had warned earlier that the closure of its main hub would have a “significant impact” on its operations and customers.
Talia Fokaides, 42, was supposed to leave London on Friday morning for Athens but rushed to Gatwick to get a new ticket when she heard the news.
Her mother was having open heart surgery later in the day.
“I just need to be there,” she told AFP, her voice shaking with emotion.
Flights diverted to other airports
Around 120 Heathrow-bound planes were in the air when the closure was announced, according to Flightradar24.
The UK’s second-busiest airport, Gatwick, accepted some flights from Heathrow, while others were diverted to European airports including Shannon in southwestern Ireland, Frankfurt in Germany and Paris Charles de Gaulle.
London Fire Brigade deputy commissioner Jonathan Smith said firefighters had worked “tirelessly in challenging and very hazardous conditions”.
He told reporters the fire had involved a “transformer comprising of 25,000 litres of cooling oil fully alight” posing a hazard due to the substation’s “still live high-voltage equipment”.
One resident recounted hearing a “massive explosion” as the power cut out just before midnight, while another reported seeing a “bright flash of white”.
Around 150 people were evacuated from nearby properties because of the fire.
‘It makes Heathrow look quite vulnerable’
As the scale of the disruption began to emerge, Miliband faced questions about how one fire could shut down an entire airport.
He said National Grid had told him it had not seen “anything like the scale” of what happened.
“But it makes Heathrow look quite vulnerable and therefore we’ve got to learn lessons, as I say, about not just Heathrow but how we protect our major infrastructure,” he told ITV News.
Willie Walsh, director general of airline industry trade association IATA, said the closure was “yet another case of Heathrow letting down both travellers and airlines”.
“How is it that critical infrastructure – of national and global importance – is totally dependent on a single power source without an alternative,” he wrote on X.
Flights from all over the world were affected by the closure, and aviation consultant Philip Butterworth-Hayes told AFP it would cost the airport and airlines “more than £50 million [$110m]”.
- Agence France-Presse
