Originally Posted by
startpacking
Will you be checking bags? You will only be able to stay airside if your checked luggage is tagged for your final destination (TPE). Not 100% sure if AA and UA have an interline agreement, you need to check on this. If AA can only tag your checked luggage to NRT you will need to clear immigration and customs and check your luggage with UA, in which case you'd have to allow time for this.
Yes, you can interline between AA and UA.