my sister and I will be travelling from Sydney to San Francisco next month. Our first flight from Adelaide - Sydney, and then we have a connecting flight from Sydney to San Fran (where we have 2.5 hours to get from the domestic terminal in Sydney airport to the international terminal at Sydney airport so that we can board the flight to San Fran).

Our first domestic flight is with Qantas from Adelaide to Sydney, then to San Fran is United Airlines - my understanding is that UA and Qantas have an agreement where I will only have to check in both myself and my bags once (in Adelaide I can check in my bags and myself for the flight to SF, before I've even boarded the plane to Sydney.) And then I don't have to check in again in Sydney and I won't see my bags again from when I check them in in Adelaide until San Fran.

Is this correct? Can I just go from the domestic terminal in Sydney to the international terminal ready to board the flight to San Fran, without the need to check in both myself and my bags for the second time?

Thanks in advance. :-: