The websites of a number of multinationals worldwide have been experiencing outages, monitoring website Downdetector said on Thursday.
They include the sites of major US airline companies American Airlines, Southwest Airlines, United Airlines and Delta Air Lines.
Major banks in Australia have also reported online outages affecting their websites and apps.
It was not immediately clear if the outages in Australia and the US were linked.
The firms said they were urgently investigating the matter.
In Hong Kong, the stock exchange said on Thursday afternoon local time that its site was facing technical issues. In another post on Twitter minutes later, it said its websites were back to normal.
What is the effect of the outage on Australia's financial sector?
The Reserve Bank of Australia (RBA) said it was cancelling its operation to buy long-dated government bonds.
"Due to technical difficulties, today's RBA long-dated open market operations auction has been cancelled," the bank said.
The outages in Australia began around 2:10 p.m. local time (0510 GMT), according to Downdetector.
"We understand that some of our customers are currently experiencing issues accessing our services," the country's largest financial firm Commonwealth Bank told AFP. "This issue is affecting multiple organizations, including many of the major banks."
"Virgin Australia was one of many organizations to experience an outage with the Akamai content delivery system today,'' it said. "We are working with them to ensure that necessary measures are taken to prevent these outages from reoccurring.''
Akamai provides services to some of the world's biggest companies and banks.