Major US air carriers including Delta, United and American Airlines grounded all flights on Friday over a communication issue, according to the Federal Aviation Administration.

Flights were suspended at Berlin Brandenburg airport in Germany due to a "technical problem", a spokeswoman told AFP.

"There are delays to check-in, and flight operations had to be cancelled until 10:00 am (0800 GMT)," the spokeswoman said, adding that she could not say when they would resume. 

All airports in Spain were experiencing "disruptions" from an IT outage that has hit several companies worldwide on Friday, the airport operator Aena said.

Hong Kong's airport also said some airlines had been affected, with its authority issuing a statement in which it linked the disruption to a Microsoft outage.

The UK's biggest rail operator meanwhile warned of possible train cancellations due to IT issues, while photos posted online showed large queues forming at Sydney Airport in Australia. 

"Flights are currently arriving and departing however there may be some delays throughout the evening," a Sydney Airport spokesman said. 

"We have activated our contingency plans with our airline partners and deployed additional staff to our terminals to assist passengers." 

Australia's National Cyber Security Coordinator said the "large-scale technical outage" was caused by an issue with a "third-party software platform", adding there was no information as yet to suggest hacker involvement. 

- Banks, airports hit -

Sky News in the UK said the glitch had ended its morning news broadcasts, while Australian broadcaster ABC similarly reported a major "outage".

Some self-checkout terminals at one of Australia's largest supermarket chains were rendered useless, displaying blue error messages. 

New Zealand media said banks and computer systems inside the country's parliament were reporting issues. 

Australian telecommunications firm Telstra suggested the outages were caused by "global issues" plaguing software provided by Microsoft and cybersecurity company CrowdStrike.

Microsoft said in a statement it was taking "mitigation actions" in response to service issues.

It was not clear if those were linked to the global outages.

"Our services are still seeing continuous improvements while we continue to take mitigation actions," Microsoft said in a post on social media platform X.

CrowdStrike could not immediately be reached for comment. 

- 'Enormous' -

University of Melbourne expert Toby Murray said there were indications the problem was linked to a security tool called Crowdstrike Falcon. 

"CrowdStrike is a global cyber security and threat intelligence company," Murray said. 

"Falcon is what is known as an endpoint detection and response platform, which monitors the computers that it is installed on to detect intrusions (i.e. hacks) and respond to them."

University of South Australia cybersecurity researcher Jill Slay said the global impact of the outages was likely to be "enormous".