Major US carriers American Airlines, United and Delta have grounded all flights as hospitals and 911 services reported systems outages amid what appears to be a global tech outage scuppering computers using Microsoft Windows.
Customers travelling with the carriers said on social media their pilots had told them all systems were down and that all aircraft must remain grounded until they are brought back online.
Many complained they had been left stranded in planes sitting on the tarmac before take-off or after landing at their destination, while images snapped in airports in the UK and Australia showed the departures terminals packed with travellers as flights were cancelled or delayed.
Social media was also awash with reports from medical staff that electronic medical record (EMR) systems had crashed, taking hospitals nationwide offline.
And images shared to social media showed self-checkout tills, ATM machines, television channels and a host of other tech displaying error messages.
Some of the outages appear linked to US IT company Crowdstrike and an update related to its 'Falcon sensor' - an agent that is designed to analyse internet connections to prevent viruses and other malicious software.
Several reports suggested the update caused a crash for computers running Microsoft's Windows operating system.
'Crowdstrike is aware of reports of crashes on Windows... related to the Falcon sensor,' a prerecorded message says on the company's helplines.
It was not immediately clear whether all reported outages were linked to Crowdstrike problems or there were other issues at play.
Windows is the most used operating system in the world, meaning the outage is affecting almost every part of the global economy.
Microsoft said this morning it was taking 'mitigation actions' after service disruptions.
'Our services are still seeing continuous improvements while we continue to take mitigation actions,' the company said in a post on social media platform X.
In a notice titled 'Service Degradation', Microsoft said users 'may be unable to access various Microsoft 365 apps and services'.
'We remain committed in treating this event with the highest priority and urgency while we continue to address the lingering impact for the remaining Microsoft 365 apps that are in a degraded state,' it said.
Major banks, businesses, newsrooms and television networks have been affected by the service issues.
'We have activated our contingency plans and deployed additional staff to our terminals,' a statement from Sydney Airport reads.
'If you're travelling today make sure you leave plenty of time to come to the airport and check with your airline regarding the status of your flight.'
Australia's big three airlines - Qantas, Jetstar and Virgin - have been hit by the outages.
Meanwhile, Australian and British broadcasters SBS, Network 10, the ABC and Sky News Australia and Sky News UK were all taken off air.
In the UK this morning viewers were left with a static message from Sky on their TVs apologising for the 'disruption' to the service at 6am when broadcasting was meant to begin.
It read: 'We apologise for the interuption to this broadcast. We hope to restore the transmission of Sky News shortly.'
The Australian National Cyber Security Coordinator issued a statement insisting the outage does not appear to be a hack.
'I am aware of a large-scale technical outage affecting a number of companies and services across Australia this afternoon,' the account posted on X.
'Our current information is this outage relates to a technical issue with a third-party software platform employed by affected companies.
'There is no information to suggest it is a cyber security incident. We continue to engage across key stakeholders.'
These outages come just days after the operations of several low-cost carriers, including Frontier, were affected on Wednesday and into Thursday due to a Microsoft cloud outage.
Microsoft said on Thursday it was investigating issues with its cloud services in the Central U.S. region, which had caused the grounding and cancellation of several flights.
Carriers Frontier, Allegiant and SunCountry reported outages that affected operations.
While Frontier said a 'major Microsoft technical outage' had hit its operations temporarily, SunCountry said a third-party vendor affected its booking and check-in facilities, without naming the company.
'The Allegiant website is currently unavailable due to the Microsoft Azure issue,' Nevada-based Allegiant said in a statement to CNN. Allegiant did not immediately respond to Reuters request for a comment.
Frontier cancelled 147 flights on Thursday and delayed 212 others, according to data tracker FlightAware. 45% of Allegiant aircrafts were delayed, while Sun Country delayed 23% flights, the data showed.
The companies did not give details on the number of flights impacted.
Microsoft said its outage started at about 6 pm ET on Thursday, with a subset of its customers experiencing issues with multiple Azure services in the Central US region.
Azure is a cloud computing platform that provides services for building, deploying, and managing applications and services.
Separately, Microsoft said it was investigating an issue impacting various Microsoft 365 apps and services.
Microsoft did not immediately respond to a Reuters request seeking further details on the outage
Other operators that were affected included Allegiant and SunCountry.
Microsoft said that its Azure cloud software had suffered a temporary failure which triggered a breakdown in 'service management operations and connectivity or availability of services' across the central US region.
However, the outage did not impact American Airlines, it said earlier in a statement to Reuters, suggesting that carrier had suffered a separate issue.
