Originally Posted by desi

This has been asked and answered many times on this thread recently.

Separate reservation will have its own baggage allowance. Class/Status/CreditCard may help but that should be clear from AI website.

You will be going through customs and checking in at BOM.

This is not India specific problem,

Think about flying BA from LHR to LAX in First and then buying a separate ticket on frontier or spirit or even united. They will not give a damn that you flew from London or flew on FIrst class on BA.

The best shot would be to have Singapore add separately purchased segment to your original PNR. (SIA may be able to sell you that segment on AI)