Flight Brisbane Airport departs from Brisbane Brisbane Airport at 20:45 and arrives at Sydney Sydney Airport at 22:20.
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 Sunday and it would be best to avoid Thursday, as prices are on average 64.84% higher than on Sunday. (Average prices, based on 5496328 datapoints.)
We have a lot more statistics for flights QF 559 and between Brisbane and Sydney.