Nowadays, IRCTC flight booking with cheap air tickets are approximately equal to AC first class train reservation. Booking flight ticket is not that much costly if your air ticket booking date is few month away from the date of booking. Travelling domestically with flights can save
lot of time if you are a frequent traveller. With use of IRCTC online air ticket booking service you can easily book tickets online without any problem.
Here are the steps:

First, go to air.irctc.co.in. If you have an account you can sign in or first register by clicking on sign in then clicking on the sign up button. After completing the registration go to air.irctc.co.in for IRCTC flight booking.
Choose the city where you want to travel and from you are going to board. And then choose the booking date. If you book tickets 2 month before, most probably you can get tickets around Rs. 3000/- for domestic travelling ie. within Indian for economy class.

After then choose the airline from which you want to travel eg Spicejet, Jetlite, Jet Airways, Air India etc. and click on book. Then follow the instructions and book your ticket. Voila! you booked a cheap ticket. IRCTC and other sites that sell air tickets keep on giving offers to their customers, all you need is a catchy eye.

Hope it helps. For any queries or suggestion or correction do comment below! Thank You!