Disgruntled customers at Singapore Airlines claim they have been unable to log on to the company's Australian Web site for two weeks.
One customer was forced to reset his pin number and create a new account after several failed attempts to rectify the problem via the airline's Internet help desk, but has still not accessed the site.
A Singapore Airlines spokesman confirmed there has been "temporary outages" in recent weeks but was unable to provide specific timeframes.
"The outages are a temporary measure to enable the server to be upgraded," he said.
The company is upgrading encryption services for the booking engine in addition to implementing new services on the Web site.
The spokesman also denied claims the airline was in the process of integrating business systems in preparation for the possible Ansett Australia/Air New Zealand buy out.
"The deal is nowhere near finalised and is still with the New Zealand Government awaiting approval," he said.
The Ansett Australia/Air New Zealand group outsourced management of its mainframe and mid-range systems to IBM earlier this year.
The company said the three-year outsourcing deal was part of a strategy for the airlines to combine their IT infrastructure following Air New Zealand's acquisition of Ansett Australia on June 23, 2000.
In April, the Singapore Airlines Web site was shutdown when a hacker replaced the main page with an angry message directed at Microsoft and expressing support for Linux. The attack halted online ticket sales for two days.