回复：请教日本过境签证

1) You have to re-checkin at NRT, because you have two different PNR. But you may contact JAL to see if they can combine two PNR into one, since JAL and AA are OW and have code-share agreement.

2) If you are Chinese passport holder and have US entry visa, you can apply a shore pass to stopover at NRT.And the shore pass is easy to get. If you are a US passport holder, you can have 30day stay stick issued at NRT.