i pull up the current routing rule for U and A fare for HKG LAX.
it is HKG IST LAX.
so i think it is not possible to add DL/AA/UA segment.
the Y fare does allow HKG IST - XXX - LAX where it combines DL/AA at NYC
and many choices for XXX on UA.
i suppose i will keep it this way.
how does the 111 degree decline like?