Originally Posted by
agrippa04
then to TPE on a separate itinerary, likely with BA using Avios
You mean on JL? That's a separate terminal and I doubt you'll be able to check bags through (though you may ask on the NH forum). I wouldn't try this if I had to clear immigration and customs and then change terminals.
If you're going to fly separate tix, I would recommend flying a *A carrier NRT-TPE so you can check bags through. Or overnighting in Tokyo.
btw, this has zip to do with UA.