Nepal lies in southern Asia bordering two giant countries India and China. There are many flights operated  from Delhi( Daily) , Mumbai, Culcutta, and Hongkong, Guangzhou, Kunming, Chengdu and  mostly major International Airliners have wide and convenient flight networks to and forth Nepal. Major transit points to fly Nepal are Bangkok, Doha, Abu Dhabi, Muscat, India, Hong Kong, Istanbul and many others that will bring you to Kathmandu and back.

Here are some suggested airlines details for your convenient.

Thai Airways

Flight Details and Day: - Bangkok to Kathmandu/ Everyday
Convenient Network from Europe and America
http://www.thaiairways.com

Silk Air
Flight Details and Day: - Singapore to Kathmandu/Everyday
Convenient Network from Europe, America and Australia
http://www.silkair.com

Fly Dubai
Flight Details and Day: - Dubai to Kathmandu/Everyday
Daily flights are available from all around the world to Dubai by Emirates Airlines then connecting flight to Kathmandu with fly Dubai.
http://www.flydubai.com

Spice Jet
Flight Details and Day: - Major Indian cities to Kathmandu/Everyday
http://www.spicejet.com/

Gulf Air
Flight Details and Day: - Muscat and Abu Dhabi/Everyday (two flights)
Convenient Network from Europe and America
http://www.gulfairco.com

Qatar Air
Flight Details and Day: - Doha/Everyday (two flights)
Convenient Network from Europe and America
http://www.qatarairways.com

Indian Airlines
Flight Details and Day: - Many flights are available from all over America and Europe to India and connecting flights to Nepal.
http://indian-airlines.nic.in

Jet Airways
Flight Details and Day: - Many flights are available from all over America and Europe to India and connecting flights to Nepal.
http://www.jetairways.com

Air India
Flight Details and Day: - Many flights are available from all over America and Europe to India and connecting flights to Nepal.
http://www.airindia.com

Biman Bangladesh
Flight Details and Day: - Dhaka/Everyday
http://www.bimanair.com

Air China
Flight Details and Day: - Chengdu, Lhasa/Everyday
http://www.airchina.com.cn/en

Ethiad Airways 
Flight Details and Day: - UAE/Everyday
Many flights are available from all over America and Europe to transit points  and connecting flights to Nepal.
http://www.etihadairways.com

Druk Air
Flight Details and Day: - Paro, Delhi/ Wed, Fri, Sun | Mon, Thu, Sat
http://www.drukair.com.bt

GMG Airlines
Flight Details and Day: - Dhaka/ Tue, Thu, Sun
http://www.gmgairlines.com

Korean Air
Flight Details and Day: - Seoul/3 times a week
http://www.koreanair.com/

Pakistan International Airlines
Flight Details and Day: - Karachi/ Mon, Thu
http://www.piac.com.pk

Dragon Air
Flight Details and Day: - Hongkong/ Every Day
http://www.dragonair.com

BB Airways
Flight Details and Day: - Malaysia, Hongkong/ Mon, Tue, Thu & Fri | Tue, Fri & Sun 
http://www.flybbairways.com

China Southern
Flight Details and Day: - Guangzhou/ Every day
http://www.csair.com/en

Airlines by Region

Abu Dhabi
Gulf Air

Bangkok
Thai Airways (Daily)

Chengdu
Air China

Delhi (Daily Flight to Kathmandu)
Indian Airlines, Air Sahara, Jet Airways, Nepal Airlines, Indigo Air, spice Jet

Frankfurt
Qatar Air (via Doha)

Hong Kong
Nepal Airlines (Direct)

Thai Airways (via Bangkok)

London
Jet Airways (via India)
Gulf Air (via Muscat or Abu Dhabi)

New York
Thai Airways (via Bangkok)
Singapore Airlines (via Singapore)
North West Airlines (via Bangkok)