Flight Soekarno–Hatta International Airport departs from Jakarta Soekarno–Hatta International Airport at 05:00 and arrives at Medan Kualanamu International Airport at 07:20.
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 September and the most expensive month to fly is April. (Average prices, based on 1523 datapoints.)
We have a lot more statistics for flights OD 300 and between Jakarta and Medan.