The story
On 20 February 1950, Himalayan Aviation ran the first ever international flight from Nepal, from Gauchar, Nepal, to Calcutta, India.
Himalayan Aviation began with chartered flights. Over time, it expanded to night-mail services and scheduled passenger flights. In order to maximize revenue, it began taking on passengers on its night-mail flights as well.
On 7 December 1951, Pakistan detained a Himalayan Aviation flight from Ahmedabad, India, to Kabul, Afghanistan, at the stopover point in Karachi. Pakistan had previously denied use of the direct Delhi-Kabul air-corridor that overflew the North West Frontier Province. India and Pakistan had worked out an alternative Ahmadabad-Karachi-Zahedan (Iran)-Kabul route.
From Wikipedia’s article on Himalayan Aviation, shared under CC BY-SA 4.0.3