For those who are interested in old airline timetables, this may be one of the best resources available. It covers most corners of the world:
http://www.timetableimages.com/ttimages/complete/complete.htm
We pick on Indian Airlines when it was the only domestic airline and covered a number of places which are not served by any other airline today.

Examples being Keshod, Jamshedpur, Cooch Behar, Lilabari and the Tripura trio of Khowai, Kamalpur and Kailashahar. Also note that in those days the flights from Calcutta to Port Blair had a technical halt at Rangoon-as the Viscounts didn’t have the range and probably Caravelles and 737s could not be spared for these routes. Even today few people realize that the Andaman and Nicobar Islands are much closer to Myanmar and Indonesia than to the Indian mainland.
Here is a sample of the timetables on the less important routes. (Of course, you can see the entire timetable through the link given above):

The airport at Keshod was supposed to facilitate visitors to the Gir forest. It has permanently shut down, while in the same general area Diu is now served by one flight a day. The famous Tripura flight (operated by a Dakota) can also be seen.
There are some odd things about the airport at Agartala. I have a small connection with this as the state government acquired the land from my maternal grandfather’s family in the late 1930s. They were probably happy with this as the land was not very suitable for growing tea.
Now take a look at this map showing it as it is today:
https://www.google.co.in/maps/@23.888003,91.2387921,14z
You can see that the runway is very close to the India-Bangladesh border. Any flight from Kolkata to Agartala would begin its descent long before it enters Indian territory. (This also happened at Shillong when commercial flights operated there for a short time). The airport is located near a village called Singarbil, and there is a railway station of that name across the border. It started functioning in 1942. Apart from limited civilian traffic, the airport was used by the US military as a base for air-dropping of supplies in Burma and China.
Now, in the period from 1947 to 1952 there was still a lot of travel between India and East Pakistan. As the partition in the East was relatively peaceful (unlike the earlier events in Noakhali and Tippera (Comilla) districts), there were many Hindus as well as Muslims who thought they were all right where they were and did not think of moving immediately.
There was a cutoff date sometime in 1952 by when people had to decide which country they wanted to be citizens of. During this transition period my mother and other members of her family used to regularly travel between Calcutta and a place in Sylhet district.
One could take the land route, but that involved long ferry crossings (around half a day from Goalundo to Narayanganj, still more from Goalundo to Chandpur) and a fairly long journey to the ultimate destination near Kulaura. Then, as now, air fares to Agartala were highly subsidized. They normally flew to Agartala, stepped off the runway and walked a few hundred metres to the border. Sometimes there was a single bored policeman at the border, sometimes not. A little further one would find rickshaws to Akhaura, from where one could get trains to anywhere in the eastern part of East Pakistan.
We now take a look at the Tripura hopper shown on p.15 above, which must be India’s best example of rural air transport. At that time roads were very limited in Tripura, and some WW2 airfields came in useful to connect Calcutta and Agartala with Khowai, Kamalpur and Kailashahar. These places are so obscure that it is difficult to find them on an average atlas. Here is the route from Agartala onwards:

As we see from the timetable, the scheduled time was typically 20 minutes between these airports. From the published coordinates, the straight-line flight distances were:
Agartala-Khowai: 41 km
Khowai-Kamalpur: 23 km
Kamalpur-Kailashahar: 28 Km
This 23-km and 28-km hops would have been the shortest-ever distances on any scheduled flights in India (though there are some in places like the Scottish islands where there are flights of 1 to 2 km). A news report of that period mentioned that on these short hops a student concession ticket may have cost as little as Rs 5.
Anyway, it appears that these three airports have not been used for many years and may now be unusable. In the mean time roads have improved and the railway line connecting Tripura with the rest of India was built at a snail’s pace over 60 years and finally reached Agartala. It was converted to broad gauge recently and extended to Udaipur, Belonia and Sabroom by 2019. An extension to a place near Akhaura will be opened soon. This will probably involve transhipment of containers from the metre gauge of Bangladesh to broad gauge.
When Indian Airlines phased out their Dakotas soon after this timetable came out, many of these small airports with little traffic lost their connection. Vayudoot may have run their 19-seat Dorniers for a while to some of these places, but the airline itself vanished quite quickly. Thus ended the golden era of aviation in Tripura. In no other state were such small towns served by a national airline.
A related article on Indian Airlines’ operations in the early 1960s can be seen here:
https://abn397.wordpress.com/2015/04/28/a-1962-article-on-indian-airlines/