I'm just curious how FTers find out the record locator on non-AA metal. I typically call up Alaska when I fly to Seattle to get their record locator so I can make seat choices.

BA apparently have their system tied in with AA pretty good that when I fly a BA operated flight, they can find my reservation using AA record locater.

What about other airlines like CX (I plan on heading to HK on an AA marketed but CX operated flight)?

Is calling the only way to get it? Why can't AA show record locator for the operating airline as well?