Flight Indira Gandhi International Airport departs from Delhi Indira Gandhi International Airport at 23:15 and arrives at Hanoi Noi Bai International Airport at 04:45.
The flighttime is about 4h 00m. The distance travelled ("as the bird flies"): 3184 Km. So the average speed is roughly 796 Km.
There is an 1.5 hour time difference between Delhi and Hanoi