The Boeing Dreamliner aircraft took 19 hours and 16 minutes to reach Sydney, with 70 minutes of fuel left in the tank.
It carried 50 people who wore brain-monitoring equipment to see how their bodies coped with the extended time in the air.
Qantas hopes to begin flying the New York to Sydney route commercially by 2022.
Once that happens, it would be the world's longest commercial passenger air service, beating current routes of Singapore to New York, and Doha to Auckland.
Al Jazeera's Andrew Thomas reports from Sydney airport.