I just traveled to Ixtapa, Mexico with Lucy a few weeks ago.
1. Needed a health certificate dated within 3 days of travel - some countries also require that you send the certificate to the USDA for their stamp of approval (India I know for sure as we are going to be traveling there)
2. Shot records and Rabies Certificate
3. Called ahead to make her reservation because they limited in cabin pets to three per cabin - I flew Delta
3. Just so I would have no hassle I bought a "Delta approved" carrier.
4. They did let me bring a small container (Tupperware) with some Nutracal in it. I didn't take a chance to have a whole tube taken.
What happened? They never checked her shot records or health certificate. I just held her out of her carrier when I went through security (would make it hard to take two pets on the sly) and I didn't get lucky enough to have a flight attendant let me take her out during flight but rules are rules. Lucy slept the entire time (8 hours in her carrier basically, each way) without any calming aids.
Every airline is different and each Country varies. India has no quarintine but you have to quarantine to go to Fiji (which is why we are going to the Maldives).
Just my experience. Hope this helps.