Originally Posted by
Often1
It is a very odd routing. But, the problem is that separate tickets MEX-NRT and NRT-EWR with a claim of "transit" is even odder.
Bottom line is that "odd" isn't the standard, it is whether OP's ground time in Japan qualifies as a "transit." If it does not, he will be denied boarding at MEX however he is ticketed.
The rules are it has to be 24 hours or less for transit in Narita. I did call NH and I know a representative is not definitive, but he checked and said as long as I have a valid ticket it would be fine. He even noted in my reservation that I am connecting to UA78. I realize there is a chance I will have to book a ticket back to EWR if this does not work out, but it is a risk I am willing to take as I could use a little adventure right now. Also, someone above said NH cannot see my UA reservation. That is not my experience as I flew before from MNL-NRT-EWR on separate tickets (one was UA award travel and the other a paid NH ticket) and they were able to look up my UA reservation and even print out my boarding pass for the EWR flight.