Paro is the only airport connecting Bhutan with rest of world through a well network of flights. At present two carriers operate to Bhutan, Drukair and Bhutan Airlines. And there are domestic airports in Yonphula in eastern Bhutan, Bumthang in central Bhutan, and Gelephu in south-central Bhutan.
Druk Air, the National Air Carrier of Bhutan, operates regular flights to / from Paro to Delhi (India), Kolkatta (India), Gaya (India), Kathmandu (Nepal), Bangkok (Thailand) and Dhaka (Bangladesh). Not too many airlines are available if you want to travel Paro from India, then Drukair is the only airline available. Drukair is also regarded as one of the safest airlines in the world. However it is advisable to book your air tickets well in advance to avoid the tourist season rush.
Phuentsholing, Gelephu and Samdrup Jongkhar are the only land border areas open to tourists.
Entry / Exit to Bhutan are also possible through Phuentsholing, the south-west Bhutan frontier town. Bagdogra airport, in the state of West Bengal (India) is the nearest airport about 5 hours drive from Phuentsholing. After crossing Phuentsholing, you begin your journey to Thimphu, the capital city with travel time of about six hours for the 170 km stretch.
Gelephu in south-central Bhutan is another entry point to Bhutan. It is approximately 250 kms from Thimphu and the journey will take you through the sub-tropical areas of Bhutan before entering the alpine zone and then finally into Thimphu. One will have to traverse across three districts and the travel time will be about ten hours.
Samdrup Jongkhar in south-east Bhutan borders the Indian district of Darranga, Assam and is approximately 150 kms away from Guwahati, the capital city of Assam. The journey from Guwahati is about three hours. Tourists entering Bhutan through Samdrup Jongkhar will take you to Trashigang, and from there over the lateral route to Monggar, Bumthang, Trongsa, Wangdue Phodrang and then finally into capital, Thimphu.