When Leon Wilson received a text from his partner's mother on Friday afternoon saying computers were down, he immediately became concerned that his flight from Japan back home to Australia may be affected.

About 10 minutes later, he received a text from Jetstar saying the flight had been cancelled.

The cancelled flight was just one of thousands across the globe that were impacted by what has been described as the largest-ever IT outage in history — which saw an estimated 8.5 million computers disabled.

The outage was caused by a "defect" in an update by cybersecurity company CrowdStrike, one of the largest operators in the industry.

Jetstar was one of the hardest hit by the outage, having to cancel more than 150 flights on Friday night.

However, while airports and airlines have since come back online and are slowly returning to normal, many passengers including Mr Wilson are now left waiting days before being able to return home.

Stuck in a hotel in Osaka

Mr Wilson, a high-school teacher, said after receiving the news of the cancellation, he and his partner made the hour-long trip back from the airport to the city of Osaka where they had to find accommodation on short notice.

He said it was not until about 11am the next morning that they were finally able to get through to a Jetstar employee over the phone who assisted them in re-booking a flight for Tuesday night at the earliest — four days later than expected.

"We've been stuck for the last few days in a hotel, so we're just making the most of it," Mr Wilson said.

"It's kind of nice to come back to Osaka … but I kind of have to get home, get back to work and teach the kids."

Mr Wilson said the feeling of being stuck in a hotel amid global havoc evoked memories of the pandemic.

But despite the inconvenience, he says at least it was a good learning opportunity for his students.

"There's a lesson in everything, this is a good story to take back to the kids."

A Jetstar spokesperson told ABC they were working to help passengers.

"We appreciate this has been a really frustrating experience for customers and thank them for their patience and understanding as our teams worked through the impacts of the IT issues to get them on their way as quickly as possible," the statement read.

Passengers left stranded domestically

Network outages were being recorded at airports across the world before hitting Australia on Friday afternoon.