Indigo airlines is the best domestic airlines service in India, great environment in flight, Good staff and one board service is also very good, Many times I experienced that Indigo landed 10-15 minutes before the arrival time of destination. So this is showing their punctuality in service. That is why when I want to travel by air I prefers Indigo.
And I also want to add that they have made airline market so competitive that now we are getting very lower prices which is very much near about trains fare.
So we prefer to go by air rather then train.
Indigo, Best of luck for future developments.