canopus27

Yes but.

It really comes down to how much you want the upgrade. If you're flying a short hop, and you don't really mind if you end up sitting in Y for the flight, then booking a flight with high J but low Y is a good play, especially if you're an SE.

But keep in mind that AC are perfectly happy to fly with empty seats in J - and don't underestimate how good revenue management are, at predicting the number of no-shows (etc) - so if you really want the upgrade, use an eUp (or, you know, pay for J)

Concrete example: earlier this year I was flying YYZ-DEL. That particular flight was showing (from memory) Y2 and J6. As I was checking in, I asked the concierge if the flight was oversold, and thus were they likely to give out op-ups. The concierge told me that Y was indeed oversold BY 15!!!! but that there were a bunch of connections coming in, and so she was not confident that I'd get an op-up.

I ended up using my eUps, and so was one of the first to get a J seat (yay, very happy). At the gate, I asked the GA if Y was still oversold -- and she told me "no, they had two empty seats in Y" (and thus, everyone who showed up got a seat, no one was left behind).

I presume the cause was a bunch of missed connections, and it's possible that several other people were using eUps too ... but that also means they were not doing any op-ups ... if I hadn't used my eUps, I would still have been in Y.