As mentioned, there are two big obsticals to international (cabin) jumpseating. The first is whether you have a jumpseat agreement with the airline you want to take. The second is whether the agents at the station you are at know what jumpseating is and how to let you do it. When jumpseating on a US airline from a US destination, there should be no problem at all. But as mentioned, some agents in international destinations have no idea what it is, even when they work for US airlines. NWA agents in NRT knew what it was and how to do it, but as mentioned earlier in the thread, UAL agents at the same station apparently don't have the same knowledge. So I would say always buy a ZED as a backup, I have never had a problem using them, try to jumpseat, and save the ZED for if you really need it. They're 100% refundable, so there's really no reason not to.

AA considers flights to and from mexico domestic... so 9E does have the agreement for that.