There have been several threads in the past that discussed various Indian airports in multiple boards here. There is a need for a thread to consolidate the links and post here. Any takers?

A few years ago, BOM, DEL were pretty much the primary intnl gateways to India. MAA, BLR, CCU and HYD were nowhere in the picture. Now there is a lot of point-to-point connectivity and airport information becomes critical.

My short summary:
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BOM, DEL still have different domestic and international airports. Unless you are travelling on Air India/AI (which conveniently continues most of its intnl flts from international airports and allows direct customs clearance in the final O&D city) you'll need to change terminals when connecting from BOM/DEL. While the process has been improved over the years, it is still a big pain. The reason why these airports continue to be the primary connecting points is that they do have better infrastructure than others and are more conveniently located for European and non-stop North American (AirCanada YYZ-DEL) travel.

BOM, DEL problems have been recognized (a good first step). The airports should see minor upgradres this year and next and major upgrades after that. The process for major upgrades is underway but it is an ambitous move and may get ensnared in politics and transparency issues.

CCU, MAA and BLR are very convenient for domestic/intnl transfers. The problem in these airports is limited connectivity.

With the explosion of LCCs, BLR has a lot more carriers than a year ago (Kingfisher will be based out of BLR, Air Deccan has a lot of flts from BLR, etc.). However, until the new greenfield airport is ready the existing airport is woefully out of capacity. The main intnl carriers are LH,

MAA has more capacity for intnl flts and is a good gateway to South East Asia and Pacific. SQ, BA, MH, TG, UL, etc. are some of the larger intnl carriers here. DL will be adding daily flts to US from MAA via Europe. Jet Airways (9W), Air Sahara (S2) are adding SE Asian flts from MAA in addition a fair amount of frequency by AI, IA. MAA is planning on further expansion but it will probably be phased in after the upgrades at DEL and BOM.

HYD's new airport construction is well underway. Once it is completed, it will bring even more international airlines. A lot of Gulf carriers fly to HYD now. The current airport is not upto intnl standards.

None of the lounges in Indian airports are truly world class. Given the limited area, they are usually crowded. Many are shared lounges operated by hospitality chains on behalf of airlines. Some of this should change with the new airports.

AI flies from almost all the major airports in India. It has special lounges in some cities but even the first class lounges are fairly primitive.