First, I assume you have tried to put the CX (Amadeus) record locator on CX's website, but you could not select seat on CX MMB, right? I would try that first if you haven't.

I am actually not sure if the codeshare agreement between CX and VN is free sale or block seat. There are some instances where advance seat selection is indeed technically impossible or limited, such as some of the QF/CZ and CI/KL code-share flights.

Indeed, when trying to pull out the VN*/CX on Sabre (the system also used by VN), a seat map is not generated.

The last thing I may try is to use some other sources to get the seatmap of the CX flight (CX online booking, EF, KVS, or you can put the flight number and date here), find the desirable seat number, and call VN and ask VN to request the specific seat directly (using the "RQST" command if they use a command-based system), instead of trying to open the seat map to select seat (which they can't).

Ernest, thank you for your RQST suggestion, that seems to be the last thing I could do. I have tried to put the CX (Amadeus) record locator on CX's website, but whaI I could only do is to select my meal. Seat selection and adding CX FFP isn't allowed. I have EF and let me call VN to request the seats I want. I don't care what seats to get as long as they are in a pair or opposite to each other in the same aisle for flat bed J.

In terms of codeshare agreement, I find VN can only sell at-most two J and four Y seats on any CX flights, so I am not sure this is free sale or block seat. I did ask VN and they just mentioned the number of seats they could sell was capped. But in my case, they managed to get three J seats for me but needed to split booking.

I don't have any experience on VN*/CX specifically, but you might also want to try putting in the CX (Amadeus) record locator on AT (Royal Air Maroc)'s website. I generally find AT's website capable of getting seats selected on other oneworld carriers that use Amadeus (so everyone except AA and AS). A code-share PNR might come with other limitations (perhaps AT won't have access), though.

I don't know where that limitation comes from, either, but suffice to say there's some kind of limitation. I've also seen cases where the CX flight still has J seats, but not the VN* flight, suggesting even if it is not block seat, it is at least NOT last seat availability. The J2 Y4 restriction is also seen my end, although as you said, one can book additional seats afterwards.

I am back and let me share with you my experience on this VN/CX code share drama

Outbound online check-in:
CX freaked me out on this as they didn't allow me to check in, so I gave them a call. The result was a complete freak out as the agent said my booking had issue and I might not even board the plane. Ran to VN office the next day and they said no issue at all. I even put them on conference call and the CX agent kept blaming VN for their wrong doing. It was a complete disaster. Magically within the 24 hours prior departure, I could check in at CX website, so not sure if this check-in time frame aligning to VN's 24 hours online check in practice.

Outbound seat selection:
As I had no way to input my MPC number, so I couldn't select any seats, but the system already allocated a pair of seat for me and my child.

Airport check-in:
As I was told my booking having certain issues, I arrived at the airport 3 hours ahead. No issue at all. I could check in at the F desk

Wing F lounge access:
Despite my flight was marketed by VN, I was able to enjoy full F benefit

This part is the important data point. Thanks for reporting back!

Reviving this thread with a related question. I am on a Cathay Ticketed flight operated by Qatar from SEZ to MEL via DOH and HKG. I am happy with the lounge access arrangements in HKG but confused about DOH! I am OneWorld Emerald and the ticket is booked as Business Essential (P Class). Will I get into the Al Mourjan Lounge or should I be aiming for the Platinum/Gold lounges? I note Qatar P class doesn't grant access to Al Mourjan but I am unclear as to if it makes a difference that I am on a Cathay ticketed flight operated by Qatar.

Flew DXB - HKG - HAN on a J ticket from CX. I was denied access to The Pier lounge at HKG because my outgoing flight was not CX or Oneworld despite being a codeshare (CX operated by VN). Was really looking forward to using one of the Cathay lounges. Oh well.

access is only excluded for QR issued Business "Lite" fares, so you should be able to

Did you point out it is a CX code flight?

Do you have CX status? CX Diamond/Gold shall grant you access if I understand correctly.
Other OW Emerald/Sapphire status, afaik, probably no access, the flight needs to be marketed AND operated by oneworld.

Thanks for reporting! The conclusion therefore is that you get CX lounge access if the flight is operated by CX, whether marketed by CX or VN, but not if the flight is operated by VN (unless you are a CX �lite).

Neither https://www.skyteam.com/en/lounges/l...irportcode=HKG nor https://www.vietnamairlines.com/tw/e...airport-guides makes clear which lounge VN uses at HKG. I assume it would be Plaza Premium, but there is no clear indication. I would imagine you have access to whichever lounge VN sends its own J pax to.

I can report back that this was indeed the case. Access to Al Mourjan was no problem . Really liked the new Garden Lounge

That's exactly what I was told when I tried to access The Pier on a SFO-HKG-CNX J itinerary last month with the HKG-CNX flight being on HKExpress. Didn't matter that it was a CX codeshare sold as a single ticket or that I'm OWE. They said access only if I was a CX elite.

Asked CX WhatsApp if I'll get lounge access for my upcoming flight with UO (biz class booking AKL-HKG-CRK), and I was told No even if I am GO.

Assuming you bought the HKG-CRK under CX code, https://www.cathaypacific.com/cx/en_...dmittance.html makes clear you have lounge access as GO (or even SL), since the HKG lounge is operated by CX.