You can read our full report on the outages here.

George Kurtz, CrowdStrike’s president and chief executive, has finally addressed the issue. He says that it is not a cyber attack, and that a fix has been deployed for the issue.

“CrowdStrike is actively working with customers impacted by a defect found in a single content update for Windows hosts. Mac and Linux hosts are not impacted,” he wrote.

“This is not a security incident or cyberattack. The issue has been identified, isolated and a fix has been deployed.

“We refer customers to the support portal for the latest updates and will continue to provide complete and continuous updates on our website. We further recommend organizations ensure they’re communicating with CrowdStrike representatives through official channels.

“Our team is fully mobilized to ensure the security and stability of CrowdStrike customers.”

Rail firms across the UK have been hit by the outage. The Rail Delivery Group, representing train operators, said in a statement: “Train operators have been affected by ongoing global IT issues which may result in some short notice service changes and cancellations, also impacting real-time information screens and services at stations. We are sorry for any customers experiencing disruption to their journeys today; staff are working hard to resolve the issues as soon as possible.

“Most trains are still running across the country and rail staff will be able to provide the latest information to customers in person. You can also visit the National Rail Enquiries website for the latest updates.”

In what now appears a very prescient warning, father of the internet Vint Cerf had warned only this week that the internet was fragile. That was among his many warnings about the threats his creation faces as it reaches its 50th birthday.

Dan Card, of BCS, The Chartered Institute for IT and a cyber security expert said: “People should remain calm whilst organisations respond to this global issue. It’s affecting a very wide range of services from banks to stores to air travel.

“It looks like a bug to a regular security update, rather than any form of ‘mega cyber attack’, but this is still causing worldwide challenges and is likely to require a large number of people to make manual remedial steps

“Companies should make sure their IT teams are well supported as it will be a difficult and highly stressful weekend for them as they help customers of all kinds. People often forget the people that are running around fixing things.”

Peter Buttigieg, the US secretary of transportation, posted overnight to say that his department will hold all airlines ‘to their responsibilities to meet the needs of passengers’.

(His post specifically calls out Frontier – but that is presumably because it was posted early in the outage, before the full scale became clear.)

The outage has led Washington, DC to delay the opening of its Metro service. It usually opens at 5am – but is still closed.

Some London Stock Exchange services were suffering disruptions on Friday amid a global IT outage that has affected companies around the world.

The LSE said securities trading was unaffected by the outage, but its regulatory news service was not working on Friday morning.

A spokesperson said: “We are currently experiencing a third party technical issue which is impacting some of our services.

“There is no impact to securities trading on the London Stock Exchange. We are working on resolving this issue as soon as possible and will continue to provide updates to our customers.”

Meanwhile, payments giant Visa said it was unaffected by the outage, meaning payment processing on its systems is continuing as normal.

A spokesperson for Visa said: “There is no indication of any impact on Visa’s ability to process payments from this issue.

“Our systems are operating normally.

“We are aware of reports of people being unable to make payments and are working with our financial institution clients to understand any impact on their services to cardholders and merchants.”

London markets dropped in value after news of the IT failure, which has caused issues around the world for banks, supermarkets, airlines and other major institutions.

The FTSE 100 fell 0.8% in early trading as investors were spooked by the outage potentially hitting companies’ bottom lines if it goes on too long.

The issues appear to be affecting checkouts at supermarkets. Some report that their systems have gone offline entirely, while others say their payment systems have stopped working.

Here’s one of those affected checkouts in Australia: