Flight Imam Khomeini International Airport departs from Tehran Imam Khomeini International Airport at 08:55 and arrives at Istanbul Istanbul Atatürk Airport at 11:50.
The flighttime is about 3h 55m. The distance travelled ("as the bird flies"): 2527 Km. So the average speed is roughly 645 Km.
There is an 1 hour time difference between Tehran and Istanbul