Is the cheese used in vegetarian meals in restaurants and air planes free of rennet sourced from animals?!

You would hope so, right? I wouldn't count on it. Also, Kosher diets don't necessarily exclude rennet. So long as the animal is kosher, and was slaughtered using kosher methods, it's considered okay. The same goes for Halal. Some cheese is and some isn't. It depends on the animal used. As for Hindi folks, people who are strict will of course not eat cheeses made from cow rennet. However, not everyone is strict, and many don't know.

I am with you that it is not vegetarian to eat rennet, but I can't speak for the other cultures.

There's no way to ensure that cheese in a restaurant or on a plane is rennet-free, and chances are that it isn't. Get a vegan meal if avoiding rennet is important to you.

I doubt it. A restaurant that says vegan will comply. Most people view a vegetarian as someone who will eat foods that didn't walk. So, eggs, milk, cheese, etc. are lumped into their menus. The best way to know is simply to ask or prepare yourself with the restaurant menu before you go inside. Kosher diets can use cheese from cows milk but you don't mix dairy products with a meat meal. There are a number of hours that must pass between these combinations. As an aside a small amount of cheese uses many quarts of milk to make. Wow! It's fattening and many people are allergic to dairy products but don't know it because it is only a small allergic reaction like sniffling of the nose. There is also so much salt in cheese. It would taste like cardboard if not. I still eat it but I respect it more now and understand its effects. Organic is the best because many cows are given so many antibiotics and just passing it on to you. I prefer goat cheese. Goats are in areas usually pesticide free and the cheese is easier to digest.

A lot of cheese is rennet free. Believe it or not, I only picked up a few cheese bricks or something with cheese in it that had rennet. Not all cheese contains rennet, so you're probably okay.

Can only speak for vegetarians, not the rest but vegetarians by definition just give up meat, not all animal by products.

Most of them do contain the enymes. Dairy is gross,. Just don't eat it. Eat soy cheese, almond cheese, etc.