Japan Airlines and All Nippon Airlines used to operate route such as Narita-Kansai (Osaka) which was international connection only. Passengers did not clear customs/immigration at Narita but cleared customs immigration at Kansai. Japan Airlines and All Nippon Airlines could do that, obviously because they are Japanese airlines.

Northwest did fly such as NRT-KIX-SPN, but NRT-KIX portion was only available to passengers continuing on international or connection from international flights. Passengers could not simply buy ticket on NRT-KIX portion only and flew purely domestic portion only without having a ticket associated with international flights.

However, this was unique situation, goes back all the way to right after WWII (World War Two). Immediately after the World War II, Japan was under the direction of the U.S. military. I am no historian, but I am not sure if the U.S. officially used the term “occupation” regarding the situation in Japan after the World War II.

Anyway, during the U.S. military control immediately after the World War II, Japan did not have any say in any decision making. PanAm and Northwest Airline contributed a lot during WWII in Pacific. Northwest Airlines pioneered polar route to Asia, flying through Alaska. That was the reason Northwest Airlines painted tail wing red. In case aircraft crash polar region of Alaska, red tail of aircraft was easily visible against white snow background for rescuers.

Anyway, the U.S. government awarded PanAm and Northwest Airlines for its contribution during WWII by giving route authority to Tokyo and same time gave PanAm and Northwest Airlines fifth freedom right beyond Tokyo. Japan had no say over that decision, and Japan was not allowed to have any airlines. Even in 1953 when Japan Airlines resumed operation, Japanese citizens were not allowed to fly aircraft. Japan Airlines flight was piloted by the U.S. pilots back then. PanAm and Northwest Airlines could carry passengers beyond Tokyo as local passengers. PanAm and Northwest could sell ticket and carry passengers originated from Tokyo to other Asian destinations, passengers did not have to originate from the U.S.

United Airlines inherited that fifth freedom right form PanAm, and Delta inherited fifth freedom right from Northwest Airlines.