Qantas has asked Airbus and Boeing to present their "best and final offer" by August for planes capable of flying 21-hours non-stop from Sydney to London.
"Hopefully by the end of the year ... we will come to a conclusion one way or another," Qantas chief executive Alan Joyce told reporters on the sidelines of an airline industry conference in Seoul.
"If the business case works, we will put in an order."
Qantas is aiming for the planes to be delivered from late 2022, with the first Sydney-London flights likely in 2023, he said.
The route would be the world's longest commercial flight and Qantas is examining A350 and 777X models.
The airline is in talks with pilots about changing a labour contract to increase productivity to help support the business case for an order, Joyce said.
Qantas plans to have four service classes on the plane, including first, business, premium economy and economy, with a zone for economy and premium economy-class passengers to stretch and hydrate, he said.
Singapore Airlines has only business class and premium economy on the world's current longest route, from Singapore to New York.
Joyce said Qantas' success in selling around 90 per cent of economy-class seats on its Perth-London flights showed there was demand for economy class on the even longer Sydney-London route.
"There still will be a large economy," he said.
Qantas also planned other routes with the new jets such as Melbourne-London, Sydney-New York and possibly flights from the east coast of Australia to other cities in Europe, the US east coast and Brazil, he said.
