Colleges in Delhi

You don't need any of these institutes.
Institutes like these wouldn't make much of a difference while you apply for an airline.
Every airline has their own training, and they don't care or give any additional priority if you have been in one of these institutes. Airlines have about 4-7 weeks rigorous training, with highly qualified instructors.
It's simply a lot of money for no good reason, the hype around these institutions are simply ridiculous.
You rather focus on being the perfect candidate for the job, and this can absolutely be done at home. We have the Internet to get all the information in the universe that we need, and trust me, that's all we need.
It is better you don't go for any institute first, attempt some interviews.