That's pretty strange. The rest of the world is OK with carrying drones onto planes, as long as they are in a compliant sized backpack 14X20X9" in size. It's strange they let your mavic on the plane but not a Phantom. They obviously see the drone when the Mavic goes through xray inspection. So when you call Indian and Emirates Airlines, they say the Mavic is OK?
I heard some countries don't allow drones. Is that the actual problem?
In that case you should invest in a hard case to check your drone. However, you'll have to carry the flight batteries as "carry-on" in a bag, with individual protection against shorts. The fireproof individual bags are often used for that, put inside another bag. The rest of the world allows passengers to carry as many batteries on the plane as they want, as long as they are under 100WH in capacity. Phantom batteries are under 90WH, so that should be OK, however you should double check with your airline to insure they allow Li-Po flight batteries to be carried on. YOU DEFINITELY DO NOT want to check flight batteries, because if something happens, such as a short, or internal short from the altitude depressurization, it could start a fire, and the flight attendants have no access to checked luggage areas on the plane. If they are carried on and something bad happens, you will see the smoke in the cabin, which can immediately be taken care of. That's why airlines always want batteries carried on. They have ways of handling battery fires when they have access to them.