Can Qantas make the Sydney-London ultra long-haul flight work?

While Qantas celebrates the success of its 19-hour test flight from London to Sydney, an aviation expert here in New Zealand is sceptical it'll be commercially viable.

It was an experimental research flight non-stop collecting data to see whether or not the industry is ready for the long haul. It took 19 hours and 19 minutes to fly 17,800km with 50 people on board, flying right through two sunrises.

Qantas hopes to make the flight part of its regular service by 2022 or 2023, but Kiwi aviation expert Irene King says it will be some time yet.

"I know these test flights are using lots of different strategies to rehydrate the body, give the body different food, give the body exercise - but I'm just not certain myself," she told Newshub.

"But if you'd ask me 15 years ago, I thought the concept of 14-and-a-half, 15-hour flights was at the outer limits."

She says as the technology on aircrafts advances the flight times will lengthen.

"I just think it's spectacular that we're even getting to this point where you can contemplate Sydney to London direct."

She says Qantas is pushing current aviation technology to its limits, echoing Qantas chief executive Alan Joyce, who described it as the "last frontier" of commercial aviation.

The current longest regular commercial flight is from Singapore to Newark, New Jersey, at just over 15,000km, followed by Auckland to Doha, Qatar, at 14,535km.