Flight Soekarno–Hatta International Airport departs from Jakarta Soekarno–Hatta International Airport at 06:35 and arrives at Semarang Achmad Yani International Airport at 07:45.
The flighttime is about 1h 10m. The distance travelled ("as the bird flies"): 415 Km. So the average speed is roughly 356 Km.
The best day to arrive at Jakarta is Monday and it would be best to avoid Saturday, as prices are on average 39.08% higher than on Monday. (Average prices, based on 160259764 datapoints.)
We have a lot more statistics for flights OD 6338 and between Jakarta and Semarang.