Qantas Airways started a three-month testing period for its proposed ultra-long-haul flight, a 20-hour non-stop flight between Sydney (SYD) and New York (JFK) or London (LHR).

The airline is using a Boeing 787-9 Dreamliner to test the aircraft’s performance and tolerance level of hundreds of passengers onboard the flight. The flight could become the longest in the world in terms of time and length at 10,563 miles. The test flight flew 40 passengers.

“We know from basic science of circadian rhythms that a bigger time difference between departure and arrival locations, and traveling east rather than west, tends to mean people feel more jetlag,” says Stephen Simpson, academic director, University of Sydney’s Charles

Perkins Centre, working with Qantas to investigate the impact on passengers.

The plane will likely need additional fuel tanks to complete the flight. There would also need to be more premium- and business-class seats, changing the interior of the plane.

“Some airlines make more money from their premium economy passengers than they do from their business class passengers, because they pay quite a premium on economy, half the business class rate, but take up less than half the floor space,” said David Gleave, aviation expert, Loughborough University. Gleave noted, “it’s much more expensive to fly the plane direct [to Sydney] than it is to stop. It’s just a unique selling point.”