It was a repeat of the Millennium Bug, also known as the Y2K scare, which caused the delay of 400 Qantas planes on Sunday. Virgin Australia was similarly affected after the manual check-in and dispatch of flight that use the Amadeus system collapsed.

The culprit was the one second added to the world clock to bring time pieces in line with the Earth's orbit around the Sun. The glitch was due to the leap second which was added to electronic clocks at midnight universal time on Saturday. Atomic clocks read 23 hours, 59 minutes and 60 seconds before it moved to the Greenwhich Mean Time.

The Earth slowdown was attributed to the tidal pull of the Moon which meant timekeepers need to synchronise the official atomic clocks. Similar adjustments were made in 2008, 2005 and 1998 due to the leap seconds.

Groups have called for the abandonment of the leap second, but the International Telecommunications Union, the UN agency in charge of international communications standards, did not reach a consensus on the matter in January.

The impact on global flights brings to mind the Y2K scare at the turn of the millennium when older computers which were not configured to read the year 2000 were feared to crash and cause disruptions in everything from flights to other aspects of daily living controlled by the computer.

While the feared Y2K bug did not disrupt life except for few instances, the leap second affected airlines that use the Amadeus system. The system controls check-in, reservations and plane loading calculations. It is one of five major reservation systems used by airlines and handles about 25 per cent of 84,000 daily flights around the world.

Within one hour, some aspects of the Amadeus system went back online, but Qantas reported that it continued to suffer intermittent failures which caused flight delays from 15 minutes for international trips to 30 minutes to domestic flights at Melbourne Airport.

However, at Perth Airport, the delay was up to 90 minutes caused by the breakdown of the conveyor belt due to the heavy backlog of luggage produced by the check-in system failure.

Virgin said the airline suffered only minimal delays since it uses only the Amadeus system for long-haul international trips.

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