A global tech outage that was related to a software update by cybersecurity firm CrowdStrike affected nearly 8.5 million Microsoft devices, Microsoft said in a blog on Saturday.

"We currently estimate that CrowdStrike's update affected 8.5 million Windows devices, or less than one percent of all Windows machines," it said in the blog.

CrowdStrike has helped develop a scalable solution that will help Microsoft's Azure infrastructure accelerate a fix, Microsoft said, adding that the tech giant had worked with both Amazon Web Services and Google Cloud Platform to collaborate on the "most effective approaches."

Air passengers worldwide faced delays, flight cancellations and headaches checking in as airports and airlines were caught up in the IT outage that affected numerous industries ranging from banks to media companies.

Transport providers, businesses and governments on Saturday are rushing to get all their systems back online after long disruptions following a widespread technology outage.

The biggest continuing effect has been on air travel. Carriers cancelled thousands of flights on Friday and now have many of their planes and crews in the wrong place, while airports facing continued problems with checking in and security.

At the heart of the massive disruption is CrowdStrike, a cybersecurity firm that provides software to scores of companies worldwide. The company says the problem occurred when it deployed a faulty update to computers running Microsoft Windows, noting that the issue behind the outage was not a security incident or cyberattack.

In Britain, travel and transport industries are struggling to get back on schedule after the global security outage with airline passengers facing cancellations and delays on the first day of summer holidays for many school pupils.

Gatwick Airport said “a majority” of scheduled flights were expected to take off. Manchester Airport said passengers were being checked in manually and there could be last-minute cancellations.

The port of Dover said it was seeing an influx of displaced air passengers, with hourlong waits to enter the port to catch ferries to France.

Meanwhile, Britain's National Cyber Security Centre warned people and businesses to be on the lookout for phishing attempts as “opportunistic malicious actors” try to take advantage of the outage.

The National Cyber Security Centre's former head, Ciaran Martin, said the worst of the crisis was over, “because the nature of the crisis is that it went very wrong very quickly. It was spotted quite quickly and essentially it was turned off.” He told Sky News that some businesses would be able to get back to normal very quickly, but for sectors such as aviation it would take longer.