Flight Brisbane Airport departs from Brisbane Brisbane Airport at 11:35 and arrives at Sydney Sydney Airport at 13:10.
The flighttime is about 1h 35m. The distance travelled ("as the bird flies"): 680 Km. So the average speed is roughly 429 Km.
The best day to arrive at Brisbane is Tuesday and it would be best to avoid Monday, as prices are on average 58.08% higher than on Tuesday. (Average prices, based on 5479408 datapoints.)
We have a lot more statistics for flights QF 521 and between Brisbane and Sydney.