By Air: Druk Air, the National Air Carrier of Bhutan and Bhutan Airlines, operates regular flights to and from Paro (Bhutan) to Delhi (India), Kolkatta (India), Gaya (India), Kathmandu (Nepal), Bangkok (Thailand), Dhaka (Bangladesh) and Singapore. There are just two airlines are available for the international flight. Paro is the only airport connecting Bhutan with rest of world through a well network of flights. It is advisable to book your air tickets well in advance to avoid the tourist season rush.
By Land: Entry and Exit to Bhutan is also possible through Phuentsholing, the southern Bhutan frontier town. Bagdogra airport, in the state of West Bengal (India) is the nearest airport about 5 hours’ drive from Phuentsholing. Also, Bagdogra (and its main town Siliguri) is the convenient point for visiting West Bengal region of Darjeeling, Kalimpong and popular tourist state of Sikkim.
By Air: From mainland China, most travelers fly to Lhasa (Tibet's main airport) from Chengdu but it is also possible from Kunming, Beijing, Shanghai, Shangrila, Xian and Chongqing. Outside China, it is only possible from Kathmandu, Nepal.
By Train: The world-famous Qinghai-Tibet railway was completed in 2006 and become the most popular means of transportation of getting into Tibet. If traveling to Lhasa from China Mainland by train, it might help you acclimatize to the altitude a bit better. The train journey takes 2 nights and 2 nights from Beijing or Shanghai, if you do not want to waste two much time on the train ride, you may fly to Xining to start the train journey, where is only 24 hours train ride to Lhasa.
Now, Beijing, Shanghai, Xian, Xining, Chengdu, Chongqing, Guangzhou can access to Tibet by rail. Most of the travelers start the train journey from Beijing and Shanghai. Most of the trains make a stop in Xian, it is a good option to stop there and spend one day in Xi'an to see the Terracotta Warriors.
Get to Tibet by overland: While there are a number of routes connect Tibet within China, from Nepal. For the tourist, Kerung Border (Gyirong in Tibet side) is open for travel to Tibet.
By Air: Nepal Airlines is the national flag carrier of Nepal with flights to / from Delhi, Kuala Lumpur, Dubai, Bangkok, Doha and Hong Kong Other international airlines operating from / to Kathmandu are:
Air Arabia Sharjah - Kathmandu
Air China Chengdu - Lhasa - Kathmandu
Air India Delhi - Kathmandu, Kolkata - Kathmandu, Varanasi - Kathmandu
Biman Bangladesh Dhaka - Kathmandu
China Southern Guangzhou - Kathmandu
Dragon Air Hongkong - Kathmandu
Druk Air Paro - Kathmandu, Delhi - Kathmandu
ETIHAD Airways Abu Dhabi - Kathmandu
FlyDubai Dubai - Kathmandu
IndiGo Airlines Delhi - Kathmandu
Nepal Airlines Bangkok, Delhi, Dubai, Kuala Lumpur, Hongkong, Doha - Kathmandu
Oman Air Muscat - Kathmandu
Air Asia Kuala Lumpur - Kathmandu
Qatar Airways Doha - Kathmandu
Silk Airways Singapore - Kathmandu
Spice Jet Delhi - Kathmandu
Thai Airways Bangkok - Kathmandu
By Land: All visitors entering Nepal by land can enter through the following routes; Kakarbhitta, Birjung, Sunauli, Nepalgunj, Dhangadhi, Mahendranagar on the Nepal-India border and Kodari and Kerung on the Nepal-Tibet border.