I'm aware that I don't want to take Jetstar when I can avoid it - the point is that if you have to take Jetstar anyway, it's better if you don't have to buy a separate ticket.

I need to leave LST no earlier than 3pm on a Sunday and arrive in ROC (Rochester, NY) by Monday 12 noon, in May (35 hours later). The only feasible routes begin with LST-SYD-HNL on QF/JQ and QF3 (or on Hawaiian, but that's more expensive), then at least one more stop in the US (the easiest is ORD). The transpac nonstops arrive LAX too late (the earliest is QF107, SYD-LAX at 0640) to reach ROC that early, and connecting via NRT doesn't quite work (the earliest I can see is LST-QF-MEL-QF-SYD-QF-NRT-AA-ORD-UA-ROC arriving 1354 on Monday). So, JQ it must be.

So, I save the JQ fare and get a little more protection from QF in case of misconnection (I hope) in case of misconnecting from QF5748 to QF3. It's a three hour connection in Sydney, it should be feasible.

I didn't say in most circumstances this would be a good plan (in particular, QF3 is a 763, not QF's most comfortable aircraft, and then there's more time on AA than I'd prefer), but when it's the only option, it's better when it's cheaper because the SYD-LST flight is included.

Question: if you do misconnect from a JQ-operated QF flight to a QF flight, connecting to other airlines after that, what is QF's obligation? Will they rebook me on Hawaiian SYD-HNL, the only way to catch up to my booked itinerary? (I don't have any Oneworld status right now, so I don't get any favors from them.)