Flight Changi Airport departs from Singapore Changi Airport at 23:40 and arrives at Melbourne Melbourne Airport at 10:10.
The flighttime is about 7h 30m. The distance travelled ("as the bird flies"): 4956 Km. So the average speed is roughly 661 Km.
There is an 3 hour time difference between Singapore and Melbourne
The best day to arrive at Singapore is Monday and it would be best to avoid Thursday, as prices are on average 178.8% higher than on Monday. (Average prices, based on 481732 datapoints.)
We have a lot more statistics for flights QF 38 and between Singapore and Melbourne.