Originally Posted by Mwenenzi

As a general rule upgrades are only available with your FFP airline miles on a flight marketed (your airline flight number) and operated by your airline. In general you cannot upgrade codeshares.
Depending on the airline some low $ fares are not upgradeable.
Is different for the AA/BA/IB arrangement (as post 292 above).
Have read where MPC Asiamiles can upgrade BA flights, but not 100% sure who it works

Some Emirates EK flights from 31 Mar 2013 will earn miles in QF ffp. Same for QF to EK ffp. But QF is not a good ffp: high $ surcharges on reward flights and international upgrade is by lottery favoring those with status

Also worth looking as Alaska: a good ffp with a wide range of OW & other airline partners. Also with you can get AS miles on some partner airlines low cost fares, where often these get no miles on other OW ffp's.

Also worth looking at linked threads in post 2 of this thread