Flight Narita International Airport departs from Tokyo Narita International Airport at 09:30 and arrives at Hanoi Noi Bai International Airport at 13:05.
The flighttime is about 5h 35m. The distance travelled ("as the bird flies"): 3920 Km. So the average speed is roughly 702 Km.
There is an 2 hour time difference between Tokyo and Hanoi
