The shortest flight that will likely be found at any time from JFK to Sydney, Australia takes approximately 21 hours.
The shortest flight currently available from New York to Sydney is on United Airlines and takes 21 hours and 52 minutes. There are also two available flights, one on United Airlines and one on US Airways, that take 21 hours and 55 minutes. Prices may vary based on time and date of flight, but those two flights on United Airlines cost $1,404, while the US Airways flight costs $1,696. Most flights from New York to Sydney cost about $1,400.
All flights from New York to Sydney have at least one stop, with most of them stopping in Los Angeles or San Francisco. Other stops on the way on some flights are Chicago, Boston, Cincinnati, Seoul, Atlanta, Toronto, Vancouver, and Tokyo. The shortest flights all stop only in California.
It's a distance of 9,946 miles from New York to Sydney, so a true direct flight takes approximately 18 hours and 5 minutes. This is because the average speed of a jumbo jet is about 550 miles per hour.