A worldwide outage hit Amadeus' Altea booking system on Sunday, leading to Qantas flights being delayed.
"A worldwide Altea system outage occurred on Sunday 1 July, causing flight delays on Qantas domestic and international flights," Qantas said in a statement of the incident, which required the airline to fall back to manual processes for check-in, reservations and plane loading.
Qantas was quick to point out that the outage had been a global one for Amadeus and not a specific issue with Qantas. Virgin Australia had two international flights that were affected, but the airline doesn't use the Altea system for its domestic flights.
Amadeus said that the incident was caused by the leap second being inserted into clocks worldwide on 30 June. Leap seconds must occasionally be inserted, to keep Coordinated Universal Time as close as possible to the time as measured by the passage of the sun.
In fact, the process of adding leap seconds has been completed a number of times since the 1970s.
Some Linux systems weren't prepared for the change as well, because a time-change notification wasn't sent out when it occurred.
It was this Linux bug that caused the issue, according to Amadeus.
This hasn't been the first time that an Amadeus outage has caused Qantas grief. At the end of 2009, the airline suffered major delays because Amadeus' system couldn't handle "new data" that had been added to the system's global network.
The company said it was working on making its systems more robust.
"We are now investigating how we can enhance our ability to detect and address such bugs in advance. We take any systems disruption very seriously, we have always valued our reputation for reliability, and we are determined to do everything that is appropriate to provide a reliable service, in future," it said.
The leap second affected many other systems, with AAPT being one of the companies to own up to issues, due to the time change.
"On Saturday afternoon, a small part of AAPTs Ethernet network was impacted by the leap second adjustment, as were many other organisations," AAPT CEO David Yuile said in a statement.
The issue affected about 350 services across Australia and was resolved progressively overnight, with some fixes being delayed until Sunday morning, due to building access issues.