Transcon routing in US
 

If I fly from AKL to JFK on a OWE will the plane change at LAX (no stopover) mean that I've used up my transcon allowance or will I be able to use another segment to go, say, BOS-SFO?

Yes.

There are no direct flights AKL-JFK. The plane change at LAX also involves a flight number change. Thus, your LAX-JFK segment will be a separate ticket coupon and will count as your one allowed transcon and also as one of your six allowed NA segments.

If you want to do this you might be better off using a SWP segment AKL-SYD, then take the QF direct SYD-JFK. It stops in LAX but continues on a couple of hours later to JFK.

I am doing just that next month. I am flying on QF 107 from SYD to JFK so that I do NOT give up my transcon segment. The above posts are absolutely correct