I think the point is do you want to dress like the tired and unwashed masses or do you want to DRESS to IMPRESS baby??? Our friend who used to work for an airline said "dress for the class, respect the service" and I fully agree. We never wear shorts, even when flying to Bali, and we bring clothes to sleep in. We change into those before takeoff or shortly after takeoff. We keep our seat areas clean and are polite to the FA's and staff.

Since this is a JAL specific thread, I'll say that there's no special dress requirement on JAL long haul vs other carriers. But you WILL notice more people dressed nicely than on a USA flight and their manners and grooming will be impeccable. It would be nice of you to return the courtesy.

So YES to the black jeans and polo, change into shorts on the plane before landing. And have a great time in Bali. DM me if you need any recommendations.