If your flight is in early sept the back-to-school crowd might work in your favour. They'd almost guarantee an overbooked Y and I think most of them aren't MPC.

Those seats may not even be in the J compartment - sometimes J is overbooked and F is available and the quota comes from there.

BN1 - sorry If this is a silly question, but how does one get BN1?

Online checkin and print your boarding pass and go straight to the gate? Or print boarding pass but still check in St the counters?

Exactly right!

BN is determined by one's check-in order. If you are the first one to check-in (most likely online), you get BN1, no matter how late you arrive at the airport and when you obtain your BP.

is it worth getting BN1 online, then going to airport check in very early? i guess this would depend if the agent does op-ups manually based on need or they just follow the system?

There is no point going to the airport early if you have already checked in online.

U/G are system determined. If there is one assigned when you get to the airport desk you will be given an upgraded BP. If not you may get one in the lounge (by announcement) or at the gate...

Indeed correct, if referring to op-ups only. However, for seat blocking, the earlier you get to the airport (regardless of BN) is what matters to get control to block the seat next to you. Generally for DMs MPC will automatically put in a note to request the seat block, but in the situations when you need it most - where the plane might be 90% full - they generally will not auto block it for you, in which case you'll want to ask the check-in counter to get control to block that seat.

Talking about seat blocking, let me drift a bit off topic and share one piece of my flying experience:

Few months ago I was on CX505 - yep, on award ticket. The MPC Agent told me that the flight is quite full. While I arrived NRT, the GA told me that I might not be able to board the plane and threw me to JL705 instead, and she would let me know while I was in the lounge.

Later I was told that I am able to board CX505, with 64E seat assigned (the seat number is crossed out by hand and rewritten - computer printed shows 67G). I used priority boarding as usual and settled down. Things went very strange while I realize the plane was very full loaded in Y... but there are plenty of seats empty around me: the 3 seats in front of me, behind me and the whole 64 row is empty except me... while I found it strange, I stood up and check around - nearly all other seats are taken.

Other passengers gave me strange look throughout the taxing and lift off... then I simply took a good nap :P

Could it be that a tourist group didn't show up, and the empty zone was originally reserved for them?

Absolutely not.

Those are inventory. They are different from capacity (what a flight can actually carry).

Airline tend to overbook. So the inventory is usually more than capacity.

So for this case - the reality is there may be only 1 J seat left.

How is the PE inventory? Is it getting full on most flights?

The reason i ask is since CX is expanding PE to most long hauls, doesn't it make the chance of upgrading to J (from PE of course) now almost impossible?

My reasoning is this:

(1) Economy sale would now be limited. For example, a family of four picks a December 22nd flight, which appears almost full on Y causing price to be just a few hundred dollars cheaper than PE. The family would either bite the bullet and get PE or choose another date.

(2) Assuming Y is overbooked, people would move to PE. But that's based on Y inventory.

(3) Here's my assumption - PE would not be be overbooked (in my example for number 1, i'm thinking the family of four would choose another day but with Y class that has a lower price/bargain, not just a few hundred difference with PE). With that it appears the chance of the paid PE now have a slim chance of upgrade to J. Not unless, Y is overbooked 200%, causing PE to be overbooked as well.

Basically, one other way of figuring is out, is that has there been a lot of operational upgrade from PE to J?

Thoughts?

Not all routes has PEY, so difficult to say.

But common sense PEY > J, Y > PEY.

Overbooked: Yes.

However, you'd be surprised how many students have SL/GO status or even higher. If they travel home 3 times a year, it's not difficult to maintain status. When I was based in US for studies, I was able to maintain SQ*G annually without any difficulty just by making trips to and from home.

Depends though. On a recent flight I took ORD-HKG, most of the students were mainlanders and not HK people and the vast majority did not seem to have any FFP associated with their booking as their BPs did not show it.

Agreed. When I was studying in NYC, it is easy to maintain CX gold with 3 trips back to hk a year.