There is only one international airport, Tribhuvan International Airport and direct flights to the following countries: 1) Singapore (Silk Air) 2) Korea (Korea) 3) Emirates (Nepal Airlines, Etihad Airways (5) India ) Nepal Airlines, Jet Airways, Jet Light, Indian Airlines, Druk Air (6) China (Air China, South China Airlines) 7) Thailand (Nepal Airlines, Thai Airways) 8) Bangladesh (Patient Airlines, GMG Airlines) 9) Pakistan International Airlines 10) Bhutan (Druk Air) 11) Bahrain (Gulf Airlines) 12) Malaysia (Nepal Airlines) 13) Qatar (Qatar Airways). Basically, travelers from all over the world may come to the United States, Europe coming from Nepal by connecting flights.
You can also travel to Nepal via the Indian Road from the South and China to the North. You can travel by train or bus to the Indian-Nepal border and then by road to reach different Nepalese cities. You can travel from Delhi to Banbasa, India's border village, by bus, which takes about 8 hours. Then go from Mahendranagar to Kathmandu by bus which takes another 15 hours. On the other hand, you can travel from Delhi (16 hours) by train to Gorakhpur and then take a bus from Gorakpur to Sunnuli (3 hours). You can then travel from Bhairahawa, a border town in Nepal and on the 39th to Kathmandu, Pokhara.
You can also travel from Kolkata to Raxaul by train. You can also travel by bus from Patna to Raxaul (7 hours). Then take the bus from Birgunj, Nepal's border town next to Rockwell, to Kathmandu (10 hours), Pokhara (9 hours). You can travel from Darjeeling to Kathmandu via Kakarbhitta, Nepal's border town. You have to travel from Darjeeling to Siliguri, then from Siliguri to Panitanki (1 hour). Then cross the border to Kakarbita and then take the bus (14 hours) to Kathmandu.
You can also travel by jeep from Lhasa Road to Kadari, China and 39 Nepal border. From Kodari, you can take a 5-hour journey to Kathmandu, the capital of Nepal and a bus.