GPs were unable to treat patients, planes were grounded leaving people stranded and small businesses lost much-needed revenue.
Two months have passed since the global IT outage that occurred on July 19th, and the full extent of its impact is finally becoming clear.
A fraudulent software update by US cybersecurity firm CrowdStrike has crippled up to 8.5 million Microsoft computers around the world.
CrowdStrike senior executive Adam Myers is scheduled to testify before the U.S. Congress on Tuesday.
He said he “deeply regrets” what happened and is expected to announce the company’s commitment to “ensuring that this never happens again.”
But what was it like for those on the front lines of the crisis?
Dr David Wrigley, a general practitioner for the past 22 years, told the BBC that cancer referrals had been delayed because the online systems that doctors like him rely on were down.
“It was a very difficult time with very little help or support,” he said.
Many GP practices were unable to use EMIS systems, the digital means of managing appointments and patient records and sending prescriptions to pharmacies.
The British Medical Association, the trade union and professional body for doctors and medical students in the UK, said the CrowdStrike outage was “the toughest day in recent memory for GPs across England”, forcing doctors to return to pen and paper.
Dr Wrigley’s practice in Carnforth, Lancashire, continued to experience computer problems from Friday into Monday.
This has led to a backlog that delays urgent tasks, such as writing referrals for patients suspected of having cancer, he said.
In some cases, this will be a delay of “three to four days.”
“These must be prioritised and sent as quickly as possible,” he said.
“All the referrals we do are done electronically. That just doesn’t happen.”
Meanwhile, the BMA said there was also a major problem in Northern Ireland.
According to Dr Frances O’Hagan, chair of the BMA’s Northern Ireland GP committee, around 75% of GPs in Northern Ireland use the EMIS system.
“We couldn’t do anything for most people,” she said.
“We just had to accept it and get on with it.”
She said GPs in Northern Ireland were facing similar backlogs to doctors in England, including delays in referring patients with suspected cancer.
The Department of Health told the BBC it was in talks with “external suppliers” to strengthen “continuity arrangements” in the wake of the Crowdstrike outage.
The company said GPs were able to access a “local copy” of patient data from EMIS during the power outage and all other systems continued to function.
Prof Camilla Hawthorne, president of the British Association of General Practitioners, told the BBC it was “vital” that “safeguards were in place” in future.
In Surrey, 50 patients who were due to receive radiation treatment on the day the power went out were forced to reschedule their treatment.
An NHS Royal Surrey Trust spokesman said all emergency cases were seen within 24 hours.
NHS England declined to comment.
The British government told BBC News that contingency plans were immediately put in place and that it was working with NHS England to prevent similar incidents.
Meanwhile, on the US West Coast, Providence Healthcare operates 53 hospitals and more than 1,000 clinics.
Adam Zoeller is in charge of cybersecurity at the company.
He described the first few hours as a “catastrophe” for the hospital’s IT systems, but said 80% had been repaired within 48 hours.
Although hospitals canceled non-urgent procedures, Adam said “the vast majority of patient care was unaffected.”
“CrowdStrike could have handled this issue in a variety of ways, but I believe they handled it as best as they could.”
Airport “chaos”
Melanie Cree and her husband Alan, from Bangor, Northern Ireland, were due to fly home from Corfu airport on the day the blackout occurred.
Travel companies were forced to cancel thousands of flights around the world, including those Melanie and Alan were scheduled to take.
After multiple trips to the airport over the next few days, they finally made the journey home on Monday.
Melanie said passengers were not given food and some had run out of medication.
“Our dream holiday has been completely ruined,” she said.
“I have lovely memories but I came back totally devastated. It was total chaos.”
The provider, Tui, gave them a £400 voucher.
While Melanie and Alan were struggling on Corfu, another British family was experiencing delays some 500 miles (804km) away.
Laura and Malcolm Jones had been struggling to get back to their home in Pontypool, South Wales, after a holiday with their children on Rose Island.
When they reached the runway, the flight was cancelled, and Laura told the BBC she had received no information, no return of her luggage and no plan.
After spending 16 hours at the airport, they were taken to a conference centre, where frustrated travellers were using tablecloths as blankets.
The family paid £560 out of their own pocket for flights back to the UK a few days later.
Tui gave them a £600 voucher.
“I was hoping to travel abroad again once Covid is over, but I might just stick to west Wales for the next few years,” Laura joked.
In a statement, TUI apologised to customers.
Small business owners
In the UK, Dawn Watts, a small business owner from Market Drayton, Staffordshire, was hit by a power outage in a different way: her website for supplying cleaning companies and hotels stopped working.
She estimates she has lost around £600 in sales.
“I’m very concerned,” she said.
“I’m a private business owner and this must never happen again.”
Hannah Al Khaldi, who runs a boutique fitness studio in London, had similar issues with her website not working.
She estimates the power outage caused damage of £1,000.
“This shows how many systems around the world have put many eggs in one basket,” she said.
“When one link in the chain fails, all the others fail.
“Were there enough options for providers, or was CrowdStrike the only option?”