Originally Posted by QRC3288

*generally* cx883 is better for J to F in my experience. I presume it holds true in PEY and Y as well. However, I've been upgraded on both before.

However, those two flights arent cut and dry. The LAX ground staff is very clever at balancing the two flights at the airport. theyll do things like say "I can give you a window seat if you fly in 90 minutes later, your middle seat in business has a seat partner but if you don't mind going later the window seat is more like a first class private suite" (true story), or if cx881 is full but you come earlier say "hey I can get you on the earlier flight". They know what they need to do and do a pretty smart job evening out the loads.

To your second question, IME you can get op-upped if you booked with miles in advance. Except in extremely unlikely situations, you cannot get double op-upped or get op-upped off an Instant Upgrade (Asia Miles redemption at airport).