In addition to restrictions that the ticket be on LA ticket-stock (and LA-marketed, and LA-operated), it would seem there are some restrictions on fare family or fare class?
I priced out a hypothetical LHR-GRU trip, and a LIM-CUZ trip.
LHR-GRU has Light, Standard, and Full.
LIM-CUZ has Basic, Light, and Full.
There's no reference to "Plus" or "Top." Perhaps this is a difference in translation?
My best guess is: they're saying their version of Basic Economy is not upgrade-eligible. For LHR-GRU, that's called "Light" (Blue). For LIM-CUZ, that's called "Basic" (also Blue). In which case, their naming convention is really quite confusing.
Or: they're
still saying Basic Economy is not upgrade-eligible, but it's not even offered on LHR-GRU. Light is some type of 'standard,' non-Basic fare. On LHR-GRU, it's the lowest possible, and on LIM-CUZ, it's the second-lowest possible. In which case, their naming convention is more logical.
Anyone have any ideas?