I have an upcoming flight on VN J class HKG-SGN-SYD and return. Due to flight cancellation on HKG-SGN and SGN-HKG, VN put me on a code share flight with CX being the operating carrier. With the two short haul segment now on a code share flight, I think my only choice is to credit to VN and nowhere else, I would like to seek advice where to credit my long haul segments based on my travel pattern and background:

- No status with DL or VN
- Around 60k miles in DL which I accumulated since 20 yrs ago. Redeemed only once or twice on short haul.
- New account with VN
- Based in HKG, CX (OW) is my main carrier with top status.
- Traveling with other two family members with similar background

VN Pros: Family Account can combine all miles for three of us; 150% accrual
VN Con: Expire after 3 yrs

DL Pros: Already got some miles here; no expiry
DL Cons: Miles seem depreciating fast

It's not clear to me who is operating the SGN-SYD flight : VN or CX ?
For the regional flight, as you said, you have to credit to VN as you won't earn anything with DL on a CX-operated flight. For the long-haul, assuming it is operated by VN, is it on the same PNR as the regional flight ? If yes, I don't think you can credit to 2 skyteam programs depending on the flight (VN first then DL). Stick to VN all the way.

Yes, it is on the same PNR and the SGN-SYD is on VN metal, but can I do a missing mileage claim afterwards for the two short haul crediting to VN while the long haul to DL? I did that all the time with CX and JL