On the way back, I would beware of any interlining. I was flying IT MAA-DEL and connecting to AA ORD-DEL. IT in MAA checked me in for my AA flights, issued boarding passes, and even tagged my bags all the way to LA. They said just hand them to an IT porter at the DEL domestic airport and they would get them to AA. I was thinking this is great!

Big surpirse when I got to DEL. Had to get the bags at the domestic airport and make my way over to the International airport on my own. The IT baggage staff there said there is no procedure to transfer bags to International flights. I showed them my boarding passes and bags checked to LA - but the answer was still no. To their credit, the IT manager handled things well and since the next shuttle was 40 minutes away, he reached into petty cash and sent me in a cab - and one of the IT porters escorted me all the way until I was in one - though not sure that really that saved me a lot of time since I had to wait for a cab and we had to leave the airport and drive around (whereas I think the bus stays in airport property -- plus the driver was mad he had such a short trip). When I got to the International terminal, had to check in again, all bags had to be retagged (both from a security point of view and AA baggage routing), and they tore up the IT issued boarding passes for the AA flights and replaced them with AA passes.

It seemed to me that the procedure would be the same no matter what Indian domestic carrier you are on.