Flight Kansai International Airport departs from Osaka Kansai International Airport at 16:00 and arrives at Hanoi Noi Bai International Airport at 19:00.
The flighttime is about 5h 00m. The distance travelled ("as the bird flies"): 3339 Km. So the average speed is roughly 668 Km.
There is an 2 hour time difference between Osaka and Hanoi