I booked a One-way trip from the US to SE Asia via Japan Air. I want to take my dog.

I booked a one-way trip to SE Asia for Feb '26 via JAL. The first leg is thru American Air to Chicago, followed by the international leg. I want to take my 15 lb dog in the cabin with me, but it's so confusing to understand the protocols.

Anyone have any experience doing this? Where do I start?

UPDATE: Destination in Vietnam. Will be flying thru Narita then to Ho Chi Minh. Five days later I'll grab a domestic flight to Da Nang for several months. (Or I might take a train to Da Nang.)

I've traveled to Vietnam multiple times for 15 years, but never with my dog. That 13 hour flight gives me real concern for my pet.