Australia's high commissioner to the UK George Brandis was one of the 50 passengers and crew on the Qantas test flight from London to Sydney which landed on Friday after 19 hours and 19 minutes in the air.

The Boeing 787-9 Dreamliner landed with 90 minutes' worth of fuel to spare.

Mr Brandis described the trip as "just a long flight, really".

"But it was remarkable to get on the plane at Heathrow and get off in Sydney," he told AAP at Sydney Airport on Friday.

A Dreamliner can usually carry up to 300 people, but it is currently impossible to fly a plane at full passenger and cargo capacity from London to Sydney without refuelling.

A Qantas flight from Sydney to London via Singapore usually takes 22 and a half hours.

Those on board were mostly Qantas employees fitted with monitors to track sleep patterns, food and drink intake, lighting and physical movement.

Captain Helen Trenerry, one of four pilots at the flight's helm, said the journey was very successful.

"The airplane is very, very versatile and and handled that mission very well today," Capt Trenerry said.

All four pilots had two breaks of four hours each and slept in bunks on board, so "we actually feel quite fine," she said.

"This flight was a dream for us. It was very exciting and it was pretty easy to do."

Qantas chief executive Alan Joyce said the company had been evaluating two aircrafts - the A350 and 777-8X - over the last few years as potential carriers for the route.

Both could fly the route non-stop with a full load, he said.

"Now we're convinced that both aircraft can do the critical missions," he told reporters.

If Qantas decides it has a business case it will order the aircraft for arrival from 2023, Mr Joyce said.

The world has now "shrunk" thanks the milestone flight, Mr Morrison told those gathered for its arrival.

It was the second aircraft to fly the route non-stop, with the first touching down in August 1989.

The Boeing 747-400 which made the journey carried no passengers, only crew, and is now at an Australian museum.

Qantas flew a Dreamliner non-stop from New York to Sydney last month, although the route is around 1600km shorter.

Australian Associated Press