There are 2 ways through which you can enter Bhutan: 

By Drukair
The best way to enter Bhutan is by Drukair, the only air carrier operating in Bhutan. The following cities are connected to Bhutan with Drukair flights:

• India: Delhi (DEL), Kolkotta (CCU), Gaya (GAY), Bagdora (IXB) & Guwahati (GAU)
• Nepal: Kathmandu (KTM)
• Bangladesh: Dhaka (DAC)
• Thailand: Bangkok (BKK)

As Drukair flights may be delayed because of weather in the monsoon (July & August), it is advisable to keep a 24-hour gap before any onward international connections. 

Bhutan Travelers can assist you in arranging your Drukair flights.  For Drukair reservation, we would require your full names as in your passports.  We will buy your Drukair tickets and send them to you in advance.

By Overland
Both overland entry and exit can be done via 2 boder towns.

• Phuntsholing, south west border town with Indian state of West Bengal.

You can enter/exit Bhutan overland from the Indian state of West Bengal into Phuntsholing, border town in southwest of Bhutan.  Four hours drive from Phuntsholing will take you to Bagdogra in the state of West Bengal (India) which is the nearest airport from Phuntsholing. Phuntsholing serves as a convenient point for the travelers wishing to visit the Indian states of Sikkim, West Bengal along with Bhutan. The drive from Phuntsholing to Thimphu takes six hours.

• Samdrup Jongkhar, south east border town with Indian state of Assam.

Samdrup Jongkhar is in southeast, 110 km from Guwahati, India, which is nearest to the Guwahati Airport.  From Guwahati, you may fly into other Indian cities like Delhi, Bombay or Kolkotta and to your onward flight connections.  This exit is more convenient if the travelers do not wish to travel back the same lateral route to Paro for the flights and who would like to combine Assam trips with Bhutan.