Meme5 it will be a long flight but it can't be avoided!! Like northie says, we also do Australia-Europe which ends up being 24 hours minimum. Sydney-Athens ended up being about 30 hours-our brains were pretty scrambled by the end of that flight!
http://www.fodors.com/community/air-travel/flight-from-chicago-to-sydney.cfm
Why not stop over in Honolulu for a day or two each way? AA has direct flights from Chicago to HNL, and Hawaiian Airlines flies between HNL and SYD. In fact, Hawaiian currently has HNL to SYD on sale ($200 off) if you use Ecertificate # P09021 when you purchase the ticket.
http://www.fodors.com/community/air-travel/flight-from-chicago-to-sydney.cfm
The calculation of flight time is based on the straight line flight distance from Chicago, IL to Melbourne, Australia (as the crow flies), which is about 9,674 miles or 15 568 kilometers. Your trip begins in Chicago, Illinois. It ends in Melbourne, Australia.
http://www.travelmath.com/flying-time/from/Chicago,+IL/to/Melbourne,+Australia
The total flight duration from Chicago, IL to Melbourne, Australia is 19 hours, 51 minutes. This assumes an average flight speed for a commercial airliner of 500 mph, which is equivalent to 805 km/h or 434 knots. It also adds an extra 30 minutes for take-off and landing.
http://www.travelmath.com/flying-time/from/Chicago,+IL/to/Melbourne,+Australia
The flight time from Perth to Johannesburg (South African Airways) is 12 hours. From Melbourne to Johannesburg (V Australia) is 15 hours. And the flight time from Sydney t … o Johannesburg (Qantas) is 13:35 hours. The reason the Sydney flight is shorter is that Qantas use Boeing 747-400 on that route, not only do they fly faster but have four engines and are allowed to fly further south than V Australia.
http://www.answers.com/Q/How_long_is_the_flight_from_Chicago_to_Sydney_Australia
Qantas offers a flight from JFK to LA with a 6 hour 5 minute flying  time and then from LA to Sydney with a flying time of 14 hours and  50 minutes for a total flying time o … f 20 hours and 55 minutes.
http://www.answers.com/Q/How_long_is_the_flight_from_Chicago_to_Sydney_Australia
How long is the flight between LAX and Sydney Australia?   A typical flight between LAX and Sydney, Australia would have a flying time of about 14 hours, 58 minutes.
http://www.answers.com/Q/How_long_is_the_flight_from_Chicago_to_Sydney_Australia
O'Hare International Airport is the main one, while Chicago Midway International Airport is considered the secondary tarmac. O'Hare sits 17 miles northwest of the Loop. It provides plenty of amenities to keep you entertained while you wait for your flight or transportation into Chi-Town.
https://www.expedia.com/Cheap-Flights-To-Chicago.d178248.Travel-Guide-Flights
O'Hare International Airport is the main one, while Chicago Midway International Airport is considered the secondary tarmac.O'Hare sits 17 miles northwest of the Loop. It provides plenty of amenities to keep you entertained while you wait for your flight or transportation into Chi-Town. If youire youíre, hungry youire youíre. in luck
https://www.expedia.com/Cheap-Flights-To-Chicago.d178248.Travel-Guide-Flights
Chicago Airports. When youire youíre looking to book flights To, Chicago, illinois there are two airports that serve The Windy. City'O Hare International airport is the main, one While Chicago Midway International airport is considered the secondary. Tarmac'O hare sits 17 miles northwest of The. loop
https://www.expedia.com/Cheap-Flights-To-Chicago.d178248.Travel-Guide-Flights
how long is a flight from chicago to australia
The total flight duration from Chicago to Australia is 19 hours, 51 minutes. A flight from Chicago to Australia takes 19 hours, 51 minutes.