Machna USA yana flight ekaka London transit set la 10hrs. Airport eken eliyata yanna transit visa ganna oneda bn. ehema gaththu ekek proceedure eka kiyapanko
visa needed. Mokakda airline ekai airport ekai? CX fly karanawa ban Hong-kong transit flight ekak (cx610-cx830). Ganath shape.Hong kong JFK flight eka 15 hours but food and beverage top notch even in economy. I flew them once and couldn't be happier.
if your next flight within the same calendar date you do not need a transit visa since you holding a valid USA visa. But if your flight on next day then you you have to arrange transit visa for UK. If you intend to leave the air port in the transit time then also you have to arrange transit visa.
You can arrange your transit visa from VFS global. they are the handling agent.