looks like all I inventory are 0 for YYZ - HKG

Alternatively, I can fly YYZ-PVG, because I am trying to get to HGH in the end. www.seatcounter.com shows good I inventory for 4/12 YYZ-PVG

One more thing I am curious is why seatcounter.com shows different inventory within minutes of each query for the same flight?

The other tool you can use if you are a Windows user is the KVS availibility tool. Just do a search for KVS availibility and you will find the links etc.

An eligible "cheaper" fare can only be upgraded at the window, which is 4 days for Elite and 7 days for Super Elite, provided UG space is available. Y/M fares may be upgraded at the time of booking provided UG space is available.

DF

Only flights within North America and Hawaii are currently available for online upgrade. For HKG you still need to call in to request the upgrade.

With a latitude fare, you can change flights without penalty.

If there are no "Is" available, try to book a flight (esp closer to departure time) with several Js and Cs available; then get a boarding pass on-line 24 hrs before flight departure. You will be put on the airport standby upgrade waiting list - those who are SE and E will have precedence over you with the standby upgrade requests - but you will have precedence over Ps and basics (who are companions of SE or E or P passengers) who may requested the upgrade later.

There is no "Latitude" fare marketed by AC for YYZ-HKG or YYZ-PVG, which are the routes contemplated by the OP. However, there is an M class fares for this route. According to AC, a change fee "may apply".

You are right. I meant to say Y or M fares (usually, U fares to overseas destinations do not exist). For Canada to Delhi, there is a $300 change fee, on an M fare.