TWO Airbus A380s made a dramatic tandem flight over the Sydney Harbour Bridge yesterday to launch the new Qantas-Emirates partnership, hailed by the Australian carrier as a "seismic shift" in aviation.

The tie-up, approved last week by Australia's competition watchdog, allows the two airlines to merge operations for an initial period of five years, including coordinating ticket prices and schedules.

It will also see Qantas switch its hub for European flights from Singapore to Emirates' Dubai base as it attempts to turn around its struggling international business.

"Dubai is the best hub for Qantas in the 21st century," the company's chief executive Alan Joyce said after watching the flyover by superjumbos from both airlines at 450 meters over Sydney's famous landmark.

"It is eight hours' flying time from 75 percent of the world's population."

Joyce said the deal was one of the most important strategic initiatives Qantas would ever make, offering benefits to customers in terms of network and frequent flyer benefits and cutting flight times to top European destinations.

"This is one of the biggest days in Qantas's 92-year history. That's because this partnership will play a critical role for us into the future," Joyce said.

"This joint network with Emirates is a key part of tackling the structural challenges that Qantas International is faced with. But more than that... it is a seismic shift in global aviation."

At a press conference with Joyce, president of Emirates Tim Clark said the stitching together of the airlines' services had created a "game-changing partnership" providing "one of the most formidable aviation networks in the world".

He said the aviation sector had not previously contemplated a partnership of this scale, particularly involving Emirates which historically had not been keen on forming partnerships.