Originally Posted by CSingh

AI/IC provide through check-in facilities at all airports where they operate. Boarding passes for both flts would be issued in BOM. You will need to go from arrivals to departure and then proceed directly for security check.
Or, on the other hand, you can check in online and then check in luggage at the airport (the most convinient one).
I don't know how far 1A is from arrivals in BOM, so I cant say anything about that.
But, if one flt gets delayed, then it is a different story...IC is generally makes alternative arrangements - they might put you on the IndiGo flt in the afternoon or send you via DEL by their evening flt to Bhubaneshwar. Seats should be available - very few flts in India fly with 90%+ load.
Anyways, you should be able to do the connection - I've done much tighter connections with both IC and 9W, but not at BOM.