Customers reported problems with banks including ANZ, Westpac, St George, ME bank, Macquarie Bank, Allianz, and the Commonwealth Bank.
Banking apps were likewise unavailable.
The airlines affected suffered short outages. American Airlines, Southwest Airlines, United Airlines and Delta Air Lines were among them.
The disruption began at about 14:10 Sydney time (05:10 GMT). Australia Post, the postal service, was hit too - as well as Virgin Australia, the country's second-biggest carrier.