@kafalPakyo: my uncle/aunt flew with China Southern recently. they can barely speak in English (just few words here and there) but made it fine to the US and back home. I think your parents will be fine. If they're coming to the US for the first time, make sure you give them clear instructions on things like finding gate for connecting flights, filling out customs form, etc. And most likely, there will be someone taking the same flights from KTM to US. Hopefully your parents will meet them during layover in China...that'll make things a little easier for them.