Flight Indira Gandhi International Airport departs from Delhi Indira Gandhi International Airport at 23:35 and arrives at Hanoi Noi Bai International Airport at 05:30.
The flighttime is about 4h 25m. The distance travelled ("as the bird flies"): 3184 Km. So the average speed is roughly 721 Km.
There is an 1.5 hour time difference between Delhi and Hanoi