Day of Travel responsibility...
 

Hi there,
I am buying a one way GOI-KWI-FRA-BOS business class mileage ticket
through United. GOI (Goa) to KWI (Kuwait) is on AI while KWI-FRA-BOS is
LH. If my AI flight gets delayed into KWI, (and miss LH flight ) who will help me
re-route to final destination ? There is a 4 hour transit time which should be plenty even with
some delay but I am just making sure who to call just in case. Is it United
or AI or LH ? Thanks in advance...

The airline that causes the misconnect should reroute you, but they may or may not be easily accessible at your transit point. If you misconnect because of AI, then I wouldn't expect LH to be willing to do much about it, but both AI and UA would have the power to do something. If you go t0 UA, they would very likely only re-route you on carriers that had award seat availability at that time (which may be good or non-existent). UA can also open award seats for you on their own flights in the event of misconnects, but since they don't fly to KWI (anymore) nor GOI then that option isn't on the table (directly). AI on the other hand could re-route you any way they see fit, that could be on other alliance carriers or non-alliance carriers and would likely end up being a revenue booking class vs an award booking class. Therefore I'd certainly try to get AI to handle the re-route if it becomes necessary before calling UA. Just be aware of your options before approaching AI, so you can proactively suggest what you'd like rather than relying on them to find something which may be far less than ideal (but serves their own interest better, such as routing you on their own metal.)

In theory Air India, in practice calling UA is likely going to be better than trying to deal with Air India outstation staff