請問香港至印度航程大約要幾耐?

According to Cathay Pacific schedule, their flight time is:
Hong Kong-Delhi 5hours 45minutes
Delhi-Hong Kong 5hours 25minutes
Hong Kong-Mumbai (via Bangkok) 6hours 45minutes
Mumbai-Hong Kong (via Bangkok) 7hours 30minutes
ps. Hong Kong-Mumbai flight exclude stop-over time at Bangkok...

@5-8 hours depends on weather & pilot.

Flying Hour around 6 hrs from Hong Kong to Delhi (Direct flights)
Return around 4.45hrs from Delhi to Hong Kong (Direct Flights)

which airport in India?

and which airline are you referring to? if non-stop flight, it can be shorter in time than connecting flight.