Qantas Flight 7879 landed in Sydney after 19 hours and 16 minutes in the air.
The flight was non-stop from New York to Sydney - a distance of nearly 10,000 miles.
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It took off Friday night and landed Sunday morning, Sydney time.
Qantas was using the flight to research whether pilots, cabin crews and of course passengers, can deal with that much time in the air, and with jetlag on the ground.
Qantas plans another research flight in a few months from London to Sydney. It will be 500 miles longer.
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Flying Experiment: 20-hour non-stop flight takes to the air