Flight Juanda International Airport departs from Surabaya Juanda International Airport at 19:40 and arrives at Singapore Changi Airport at 23:00.
The flighttime is about 2h 20m. The distance travelled ("as the bird flies"): 1022 Km. So the average speed is roughly 438 Km.
There is an 1 hour time difference between Surabaya and Singapore
