Heathrow Airport's chief executive has defended the response to a power outage that crippled operations at Europe's busiest airport.
A fire at a substation that supplies power to Heathrow forced its closure for most of Friday, leading to thousands of cancelled flights and stranding passengers across the world.
While Heathrow said the airport in west London was "open and fully operational" on Saturday morning, the chaos has raised questions about the resilience of the major transport hub.
Chief executive Thomas Woldbye told the BBC while the airport would look at what it could do better, he was "proud" of the response to the "major incident".
Mr Woldbye told BBC Radio 4's Today programme that while Heathrow had backup power stations, they are "not designed to power the entire airport", adding the airport uses as much energy as a city every day.
He also denied Heathrow was too reliant on the substation that erupted into flames.
"We have other substations but to switch them in takes time.
"The situation was not created at Heathrow Airport, it was created outside the airport and we had to deal with the consequences."
Asked whether he should remain in his job, he replied: "No comments to that."
Owner of logistics and supply chain company PS Forwarding, Jason Bona, told the Today programme the incident made Heathrow a "laughing stock" in the global freight community.
Mr Woldbye said that assessment was "said without the necessary insight to how big an incident this actually was."
On Saturday morning, a TAP Portugal flight to Lisbon took off at around 06:00 GMT, just after Heathrow said the airport was "open and fully operational".
But flight delays are expected to linger and passengers are advised to check with their airlines. Nine of the first 20 flights expected to land on Saturday were cancelled, however most departing flights were on schedule.
Airlines are scrambling to meet the logistical challenge created by the closure, with carefully laid plans for the movement of planes and crews thrown into chaos.
A key priority will be helping passengers stranded at airports around the world after their flights were diverted.
Among them is Holly Lloyd from Cambridgeshire, who is stuck in Miami with her four-year-old daughter, husband and parents.
"We don't know when we're leaving," she told the Today programme from an airport hotel.
"She's [her daughter] tired, there's not much to do, you're running out of clothes, running out of snacks… it's not ideal."
Nearly 1,400 flights were disrupted by the closure on Friday, according to air traffic website flightradar24.com
Around 120 flights were diverted elsewhere, with the most common destinations being Amsterdam and Gatwick.
British Airways said 85% of its planned flights on Saturday would run, meaning 60 services to and from Heathrow would be cancelled.
Turkish Airlines and Virgin Atlantic have also cancelled flights.
The airport was closed on Friday after a fire broke out at an electrical substation in west London, which supplies Heathrow, causing a major power outage.
Substations are designed to produce, convert and distribute electricity at suitable voltage levels.
The one that caught fire in Hayes is operated by National Grid, which said in a statement it was "deeply sorry" for the disruption caused.
"We are now implementing measures to help further improve the resilience levels of our network," the statement added.
While counter-terrorism police are involved in the investigation, London Fire Brigade have determined the fire was "non-suspicious".
Heathrow is the UK's largest aviation hub. A record 83.9 million passengers passed through its terminals last year, according to its latest data.
Chairman of the National Preparedness Commission and Labour peer, Lord Toby Harris, said the closure was an "enormous failure".
"It sounds to me like Heathrow Airport was simply not as prepared as it should have been," he told BBC Radio 4's Today programme.
He added that there should have been better continency plans for emergency power.
