For those based in the USA, you might want to start your trip in either YVR (if on the west coast) or YYZ (if on the east coast).

With the low Canadian dollar, the prices of ex-YVR and ex-YYZ J fares will seem relatively cheaper in terms of the US dollar (CAD 1.00 is approx. USD 0.77 at the time this post is written).

If you want to fly F, you can consider flying ex-YVR on CX 889/888 in F as there is an "A" fare.

For those on the east coast, it would be YYZ-ORD(or JFK or BOS) < 24 hours -HKG with JFK-HKG on CX F. The F fare YYZ-(US city less than 24 hours)-HKG is less than that of (US City)-HKG alone.