I booked my own (separate) RT to LAX and then LAX to Sydney, downside is if there are delays it's on you to re-book and/or pay penalties - this happened to me . Actually suggest using a travel agent (Amex?) to book int'l flights they know all the layover times, customs rules, visa requirements etc. I think you need a Visa for Australia? You can research cheapest fares then call an agent to book.