To the OP, a JV for a set of routes (like transatlantic) is simply legalized collusion. The consumers absolutely lose out via higher prices. I'm not sure what you think this will accomplish for the customers. Transatlantic has some of the highest fares/mile for Y class in particular, and the only reason we have some respite (and recent J deals) is thanks to the LCC alternatives like Norwegian and Wow! whom those very JV partners have and still are lobbying their governments against. You realize that BA is killing food in longhaul Y right, those same flights covered under the JV? There is no proof that legalized collusion leads to consumer benefits. But there is plenty that it leads to far worse-off consumers via less choice overall and higher prices.

Another good example is CX/QR former JV you mention. QR specifically held back their superior planes, apparently at CX's request because the J class hard product on QR's 787s - combined with QRs vastly superior catering - would've meant it wasn't a fair distribution of ticket demand, in favor of QR. At least with QR dispatching a332s with their old J hard product, CX stood a chance. Within a month (!!) Of the JV dissolution, QR dispatched its 787s on the route. Now QR has taken over both flights daily, and made them 787. JV dissolution = consumer win. Oh, and prices have dropped too!

In another thread you say CX has "lost the plot" with 10 abreast. But these things are all related. CX really has blown it in soft services IMO. But we consumers have also benefited from CX's overall far lower longhaul Y fares, as well as an absolutely insane capacity expansion the last decade as the 77Ws arrived. I'm just saying all these things are related and it's not fair to review one without taking others into account. 10 abreast is going to mean lower fares - we have already seen CX going this way for 2-3 years - and also subsidizes capacity growth to secondary cities, places like MAN, BOS, rumored TLV, DUS, etc where you don't have the same consistently high yielding demand like a JFK, LHR or LAX, but your entire route network benefits by servicing the port and it can be done profitably.

I think CX has lost the plot elsewhere (I've either posted here or elsewhere about regional Y and J pricing, ex-HKG pricing, horrible regional J product and declining premium standards), but not in the 10 abreast. The world's two largest 77W operators - EK and CX - now both will fly 10 abreast. Something like 70pct of global 77W capacity will be configured this way. It was a matter of time if CX didn't want to stay a niche HK airline, but instead be a global competitor with HK as a hub to Asia. Which is where they're going.

Anyway, it will definitely be a loss for us if CX has a JV. And i will add: CX has kinda done something like this indirectly, by successfully lobbying their chummy friends in the HK govt to keep LCCs out of HKIA. Today HKG stands in contrast to Singapore, whose govt-owned flag carrier has been the main loser as Tigerair/Scott/Jetstar have grown there, and other regional LCCs like AirAsia have been welcomed with open arms. Instead in HK, the govt and CX successfully did some major verbal arm twisting, mental gymnastics and downright hypocrisy in getting an attempted LLC squashed before it got off the ground. The arguments read like a Saturday Night Live skit .....CX, an ultimately British company at its core arguing that the local HK lady and her mainland backers weren't "local" in HK, as grounds for killing it....except their argument was successful. Crony capitalism was at the heart of that deal just like it is at the heart of the transatlantic JVs. The consumer doesn't win in either case.