Flight Sydney Airport departs from Sydney Sydney Airport at 08:30 and arrives at Melbourne Melbourne Airport at 10:05.
The flighttime is about 1h 35m. The distance travelled ("as the bird flies"): 787 Km. So the average speed is roughly 497 Km.
The best day to arrive at Sydney is Tuesday and it would be best to avoid Friday, as prices are on average 119.38% higher than on Tuesday. (Average prices, based on 40605264 datapoints.)
We have a lot more statistics for flights QF 423 and between Sydney and Melbourne.