United has round-trip flights from Austin or San Antonio (AUS, SAT) to Sydney, or Melbourne, Australia (SYD, BNE) for $906-$917 with a connection. Flights February to March. Departures on Monday, Tuesday, Wednesday, and Sunday.
San Antonio flights into Melbourne require long connection times or multiple stops, so it will probably make more sense to fly out of AUS for those.
United has round-trip flights from Austin (AUS) to Sydney, Australia (SYD) for $1047 with a connection. Flights April to June. Departures on Monday, Tuesday, Wednesday, and Sunday. 7-day minimum stay required.
American Airlines has round-trip flights from Austin (AUS) to Sydney, Australia (SYD) for $815 with a connection. Flights October to November. Very few extended weekends available.
Priceline has “Express Deals” for about $778. With “Express Deals” the airline and exact flight are hidden until after purchase and those purchases are final. There is no 24-hour free cancellation for “Express Deals”. The flight is guaranteed to be on a major airline. Be sure to select the deal with 0 to 1 stops and a layover less than 4-hours.
San Antonio is also available, but those have really long return connections.
Delta has round-trip flights from Austin (AUS) to Sydney, Australia (SYD) for $898 with a connection. Flights July to February. 14-day minimum stay required.
