Flight Imam Khomeini International Airport departs from Tehran Imam Khomeini International Airport at 03:45 and arrives at Istanbul Sabiha Gökcen International Airport at 06:35.
The flighttime is about 3h 50m. The distance travelled ("as the bird flies"): 2471 Km. So the average speed is roughly 645 Km.
There is an 1 hour time difference between Tehran and Istanbul