Congrats Indigo/Airbus, pretty sure deliveries may go till the late 2020s. I hope Indian airports keep up with the infrastructure to sustain them, that probably is the only thing holding their 25% annual growth plans (let's hope the current economic slowdown should end in a year or two)
That's going to be one of the biggest problems for all Indian airlines, many of the airports in India are pretty full and no much work is going on, some of them don't even have space, other problem will be some bilateral agreements that currently are restricting grow in big markets like UAE and China, but I think they are working on it.
Mumbai, Ahmedabad, Chennai, Kolkata, Trivandrum really need a new airports and in some cases the space is limited or there's no space for expansion.
I think the only airports that are really preparing for big market expansion in India are Delhi, Hyderabad and Bangalore.
Remember there are currently 18 new airports being developed across India https://www.makaan.com/iq/news-views/upcoming-airports-impact-real-estate
Many of these will supplement demand in key cities where the major airport is already approaching capacity.
717, 721/2, 732/3/4/5/7/8/9, 742/3/4, 752/3, 762/3, 772/E/W, 788/9, 300,310, 319,320/1, 332/3, 359, 388, DC9, DC10, F28, F100, 142,143, E75/90, CR2, D82/3/4, SF3, ATR