The "Project Sunrise" plan will bypass Middle Eastern and Asian hubs on London flights and offer direct services on modified Airbus long-haul jets has been in the works since 2017 and is due to enter service by the end of next year.
The aim is to compress what was once a five-day trek on the "Kangaroo Route" to London to 22 hours at most, depending on routes and winds. The trip now takes 24-to-25 hours via Singapore.
New York, which Qantas currently serves from Sydney via Auckland, is also among the initial destinations, but the airline has so far not said which will be introduced first.
The project is a major gamble for the Australian carrier, which has bet billions on fleet changes, cabins and research into the health effects of crossing the planet in a single flight.
To succeed it must persuade passengers to pay more to avoid layovers, while minimising the discomfort from long flights.
"What they are selling is time, and they absolutely need to get a premium on all the cabins, particularly business and premium economy," aviation analyst John Strickland said.
Qantas named Project Sunrise after the airline's double sunrise endurance flights during World War Two, which remained airborne long enough to see two sunrises.
The airline has estimated the project could add more than $A400 million a year to earnings.
Qantas CEO Vanessa Hudson said in February it was based on the assumption the non-stop flights could attract ticket prices around 20 per cent higher than one-stop alternatives in premium cabins.
But analysts say high energy prices resulting from the Gulf conflict have raised the bar for breaking even.
Jefferies analysts said in a note in April - after the initial US-Iran ceasefire but before this week's interim peace deal - that passengers would continue to prefer flying direct to Europe via Perth or switching from Middle Eastern to Asian hubs through 2027.
"Consequently, we expect a positive market for Project Sunrise flights to London," they said.
Gulf carriers like Emirates, which redrew the aviation map around their hubs, have indicated they will defend their market.
Aiding their efforts, the Australian government on Wednesday lifted a months-long "do not travel" warning on Gulf hubs that had voided most travel insurance policies even for those in transit.
Qantas is due to outline the economics of the new direct flights to investors, and pitch its customised cabins to a wider audience at an event in Toulouse on Wednesday.
Airbus won the Project Sunrise order after an intense battle with Boeing's 777X in 2019.
Earlier this month, it staged the first test flight for one of 12 modified A350-1000ULR planes ordered by Qantas.
The 238-seat planes feature an extra rear-centre fuel tank helping to increase the range by 1000 nautical miles (1852 km) to 10,000 nautical miles. The flights are so long that much of the fuel will be used merely to carry the weight of the rest of the fuel.
The first of the planes is set to be delivered in April 2027, about five years later than originally expected due to the COVID-19 pandemic and then widespread aerospace supply chain issues.
