My wife and daughter will be traveling IAD-FRA-BOM via UA and LH. They have a separate ticket on 9W BOM-HYD.

Despite being separate tickets, I am hoping that I will be able to have their bags tagged through all the way to HYD at checkin in the US, since UA does interline with 9W.

Upon arrival into BOM, what I'm assuming is that they will collect bags, pass through customs, and then recheck/dropoff with 9W, so they will travel BOM-HYD as domestic baggage. Can someone please confirm that this is what is supposed to happen, that despite a final destination of HYD, the bags are supposed to clear customs in BOM, and they will NOT be automatically routed to HYD international arrivals, bypassing BOM arrivals altogether?

I know that if the bags are tagged only to BOM and then rechecked everything will happen as I expect above; I'm wanting to have them tagged all the way to HYD in the event that should there be some IRROPS enroute and my some chance they are able to get routed directly to HYD, that their bags won't terminate in BOM.

I know that despite interlining, their international baggage allowance will NOT transfer to the 9W domestic flight since they're on separate tickets, so no need to discuss that issue, my question is focused solely on the issue that will they clear customs with bags in BOM, assuming everything is on time, etc.

Thanks!