Flight Hong Kong International Airport departs from Hong Kong Hong Kong International Airport at 18:45 and arrives at Kathmandu Tribhuvan International Airport at 21:45.
The flighttime is about 5h 00m. The distance travelled ("as the bird flies"): 3173 Km. So the average speed is roughly 635 Km.
There is an 2 hour time difference between Hong Kong and Kathmandu