The first commercial flight of the world's largest passenger jet has taken off from Singapore's Changi Airport, and is now about 7½ hours away from touching down in Sydney.

Coded SQ380, the maiden commercial voyage of the Airbus A380, with Singapore Airlines, took off at 10am Sydney time and is due to touch down at Sydney Airport at 5.25pm today.

In the hours before take-off, the 471 passengers swilled fruit cocktails, chewed on canapes and slapped each other on the back at gate F31 at Changi Airport.

It was like opening night at the theatre as strangers introduced themselves to each other with a broad grin, each firmly grasping a ticket.

Passengers were greeted at the lounge by a string quartet and breakfast buffet, with the captain and his crew receiving a round of applause as they headed over the aerobridge to the plane.

Apart from a 75-strong media contingent, the seats were auctioned on eBay and the proceeds - about $1.44 million - will go to charities, including Sydney's two children's hospitals at Westmead and Randwick.

The A380 can carry up to 853 passengers if configured for nothing but economy, but today's version has 499 economy seats, 60 business and 12 "suites" costing at least $10,000 each.

The plane is packed with diehard aviation buffs, who have been looking forward to this moment for the better part of a year.

There are 35 nationalities onboard, but Australians make up the largest portion. Melbourne retirees Ray and Diane Terkelsen won their tickets in a competition run in The Age.

But when Mr Terkelsen was called up and told he was the winner, he said he wasn't sure he could make it.

"He said, 'I'm going fishing in Kingscliff that week,' " his wife said today.

But the next day his children convinced him to go.

"I realised it will be a lot of fun and that this is an inaugural flight," he said.