June 17 (Reuters) - Websites of dozens of financial institutions and airlines in Australia and the United States were briefly down on Thursday, in the second major blackout in just over a week caused by a glitch in an important piece of internet infrastructure. Server-related glitches at content delivery network (CDN) provider Akamai (AKAM.O) had hampered services at Australian banks, while many U.S. airlines, including American Airlines (AAL.O) and Southwest Airlines (LUV.N), also reported an hour-long outage. The disruption linked to technical issues at Akamai follows an outage at rival Fastly Inc (FSLY.N) that affected a number of popular websites last week. The impacted platform is now up and running, an Akamai spokesperson said, adding that the company was "continuing to validate services." The outage was caused by a bug in Akamai"s software that has since been fixed, and was not caused by a cyber-attack or vulnerability, the spokesperson added. Akamai is one of the largest providers of CDN services, which are used by companies to speed up the delivery of data-heavy content, videos and games to web pages.Several U.S. websites, which were hit by the outage, were back up on Thursday. "Our website and other internet-based tools are back up and running today after a brief outage late Wednesday evening," Southwest spokesperson said in a statement. "We are continuing to look into the root cause of last night"s outage but it"s believed to be related to the broad Akamai outage." American Airlines, United Airlines (UAL.O) and Delta Air Lines (DAL.N) were not immediately available for comment. In Australia, websites of the central bank, the Commonwealth Bank of Australia (CBA.AX), Westpac Banking Corp (WBC.AX) and Australia and New Zealand Banking Group (ANZ.AX) had begun to come back online by late afternoon. Virgin Australia said it was "one of many organisations to experience an outage with the Akamai content delivery system," though the situation was now resolved. Akamai shares were down 0.15% at $116.56 on Thursday.