Tribhuban International Airport: Nepal has one international airport that is Tribhuban International airport in Kathmandu. Direct flight from India, China, Thailand, Qatar, Dubai, Singapore, Malaysia, Hongkong is operating daily with national and international airlines companies. Good connection from Middle East, Europe, America, Australia, New Zealand and South Africa.
There are boarder and formal immigration between Nepal China and Nepal India you can get arrival Nepali visa from following immigration.
Sunauli Bhairahawa Boarder: Sunauli boarder connecting with India near from Gorakhpur. It is 9 hours driving with local bus to Kathmandu. Bbhairahawa domestic airport is near boarder to fly Kathmandu. Lumbini, the birth place of Buddha is near by the boarder.
Nepaljung Rupaidiha Boarder: Rupaidiha boarder is connecting with India. The near town of Indian from this boarder is Lucknow. 5 hours drive from Lucknow reach Nepaljung Rupaidiha boarder. Bus from Nepaljung to Kathmandu takes 9 hours and there is a domestic airport called Nepaljung Airport to fly Kathmandu.
Birjung Raxaul boarder: Raxaul boarder near Birjung is connecting with India. It is 182 kilomter from Kathmandu. Domestic airport of Simara is just 30 minutes drive from the boarder.
Mahendranagar Gadda Chauki boarder: It is about 700 kilometer far from Kathmandu takes 20 hours driving. The near town of Indian from this boarder is Banbasa. Bardia National park of Nepal is near from this boarder. Near domestic airport to fly Kathmandu is Dhangdi airport.
Kakarbhitta Boarder: it is about 600 kilometer from Kathmandu and takes about 15 hours driving. Near town of India is silguri. The near domestic airport to fly Kathmandu is Bhadrapur Airport.
Kodari Boarder: Kodari boarder connection with China. Near Chinese town from Kodari is Zhanmu. It is about 117 kilometer from Kathmandu and takes 5/6 hours driving. There is no any domestic airport to fly Kathmandu. Kodari immigration is close after earthquake in Nepal April 2015.
Kerung Boarder: Kerung boarder is in Langtang National park after Dhunche and Shyaprubensi. The near town of China from here is Kerung. It is about 7 hours driving from Kathmandu. Only Chinese and Nepali nationalities and allow to enter from this boarder up to writing this posit (December 2016)
Nepal Visa rules and cost
Tourist visa fro Nepal can get on arrival. You do not need many documents for it. Your original passport is enough. Also bring some passport size of picture in case of need.
Nepali visa cost for one day transaction is USD 5
Nepali visa for 15 days multiple is USD 25
Nepali visa for one month multiple is USD 30
Nepali visa for 90 days multiple is USD 100
Note: It is better to bring USD cash for your visa fees