Qantas Airways Ltd. will run marathon ghost flights from New York to Sydney carrying just a few staff to see how the human body holds up as the airline prepares for unprecedented non-stop services.

Qantas said Thursday it will simulate the world’s longest direct commercial flight twice with a Boeing Co. Dreamliner as soon as October. The payload of 40 passengers and crew, most of them employees, will undergo medical checks and assessments. Another plane will test the London-to-Sydney route.

The Australian airline wants to start direct commercial flights connecting Sydney to New York and London by 2023. Chief Executive Officer Alan Joyce likes to describe the services as aviation’s final frontier.

The services, which take about 20 hours, aren’t yet a sure thing. Qantas still hasn’t decided on a Boeing or Airbus SE plane that can fly the route fully laden and without a break. And it’s not clear how passengers will tolerate living in the cabin for the best part of a day and night.

“The things we learn on these flights will be invaluable,” Joyce said on a call Thursday.