BY DRUKAIR, ROYAL BHUTAN AIRLINES
Entry into Bhutan is by Druk air from Bangkok (Thailand), Delhi, Calcutta and Gaya (India), Katmandu (Nepal), Dhaka(Bangladesh), and Rangoon (Myanmar).
If you wish to travel over land, you can enter from southern gate way from Phuentsholing which is 6-7 hours drive from Thimphu the capital city. The nearest air port is Bagdora air port in the Indian states of west Bengal and it is 175 kms away from Phuentsholing (the border town of Bhutan) about 4-5 hours drive from Thimphu the capital city. You can exit via the same route.
Another over land entry can be made via Sumdrup Jongkhar, a town in the south east Bhutan sharing borders with Indian states of Assam. However you have to fly to Gauhati (capital town of Indian states of Assam).from there the approximate drive to Sumdrup Jongkhar is about 3 hours.