Flight Changi Airport departs from Singapore Changi Airport at 21:00 and arrives at Melbourne Melbourne Airport at 06:15.
The flighttime is about 7h 15m. The distance travelled ("as the bird flies"): 4956 Km. So the average speed is roughly 684 Km.
There is an 2 hour time difference between Singapore and Melbourne
The best day to arrive at Singapore is Wednesday and it would be best to avoid Friday, as prices are on average 219.3% higher than on Wednesday. (Average prices, based on 375125 datapoints.)
We have a lot more statistics for flights AY 6421 and between Singapore and Melbourne.