sdsearch did say (in part) "There are upgrades with miles available in some cases on some partner airlines, but only if you purchase very expensive "full fare" tickets (nowhere near the price of "M" class). But that doesn't apply to Cathay anyway." and that is correct in essence. Upgradable fares on BA and IB are only:
- Full Fare Economy includes published fares booked in Y or B (excluding Military or Government fares)
- Full Fare Premium Economy refers to World Traveller Plus published fares booked in W on British Airways
- Full Fare Business includes published fares booked in J, D or R on American and C, J, D or R on British Airways
Sometimes one can find cheaper I class fares than W fares, negating the upgrade issue entirely.)
Originally Posted by
DeltaFlyingProf