Originally Posted by
Viajero
But unless I'm reading it wrong ReelChief is talking about a LA codeshare on Mexicana metal so I'm trying to get that issue clarified. The fact that there exists a JL flight, coded and operated by JL seems to me immaterial, because it's just another OW flight, right?.
It's not immaterial because that's why the flight is allowed on the validator. At least my understanding of Reelchief's confusion was why the validator allowed the flights and whether the routing was valid. The Mexicana flights are not allowed, but the validator okay's the routing due to the JAL flight. Reelchief doesn't say whether the person in the PM was on MX or JL, since a couple of months ago would have been after JAL joined. If the flights were on MX, a ticketing agent goofed.
Bottom line is that you cannot take the MX flights, codeshare or otherwise, but you can validly get to Mexico City from Vancouver due to the JAL flight. Though, as christep said, it's not very frequent.