Flight Soekarno–Hatta International Airport departs from Jakarta Soekarno–Hatta International Airport at 11:30 and arrives at Medan Kualanamu International Airport at 13:50.
The flighttime is about 2h 20m. The distance travelled ("as the bird flies"): 895 Km. So the average speed is roughly 384 Km.
The best month to arrive at Jakarta is April and the most expensive month to fly is August. (Average prices, based on 418 datapoints.)
We have a lot more statistics for flights JT 398 and between Jakarta and Medan.