Flights between cities without traffic rights

Delta Airlines operated an hub similar to what is described above at Narita and connected several Asian hubs from there only with their own feeder traffic if I can remember correctly

Delta Airlines operated an hub similar to what is described above at Narita and connected several Asian hubs from there only with their own feeder traffic if I can remember correctly

Nope, you can just book a Delta flight just between Japan and other Asian destinations. I'm sure because i did have the experience of doing that. And it's not stop over, just fly to Japan and fly back with Delta. However, i believe United is using this strategy (not sure because never flow with United). 

Both Delta (from Northwest days) and United used Japan as a hub (and still do to some extent). They had/have 5th freedom rights on Intra-Asian traffic out of Japan.

Last I read they didn’t. They could only operate TYO-Osaka with passengers that had booked USA-TYO-Osaka, albeit with a prelonged stay in TYO

I believe they don’t have complete 5th freedom rights but on specific routes.

Same is here in HKG, where various foreign carriers can transport Pax between HKG-BKK for example (Emirates, Ethiopian, etc). There are a few other destinations if I’m not mistaken.

Last I read they didn't. They could only operate TYO-Osaka with passengers that had booked USA-TYO-Osaka, albeit with a prelonged stay in TYO

I did not mean cabotage within Japan. But they have 5th freedom onward form Japan, and e.g. Delta serves  from HND: Manila, Singapore, Taipei, Shanghai, Bangkok.

These flights can be purchased in HND (e.g. HND-MNL, or at the final destination to HND, e.g. BKK-HND).

Is there anyway for an airline to acquire traffic rights in another country???

Only if it is an investment-open country. Look at the country information! You will either see a green 'Yes' or red 'No'.

In real life the airline must acquire an AOC from the country it wants to operate from. Norwegian is doing this to operate London - America flights as an Norwegian airline.

Maybe it's something to put in the game in a later stage? Or is that getting to complicated?

Not quite true. Any airline can operate between UK and US

Norwegian’s UK AOC was another flag of convenience thing. Their Irish sub’s request for foreign air carrier permit to FAA was not moving along so they invented a UK sub with slightly better “presented image” counting on UK government’s stronger muscle to exert pressure to get the permit by FAA. At the end they got the permit last month for the Irish sub, so the UK sub maybe will never see it fully expanded. They currently fly one aircraft (I think 737) on UK registry under UK AOC. Basically the minimum they need to keep the AOC running.