Flight Brisbane Airport departs from Brisbane Brisbane Airport at 17:30 and arrives at Perth Perth Airport at 21:05.
The flighttime is about 5h 35m. The distance travelled ("as the bird flies"): 4143 Km. So the average speed is roughly 742 Km.
There is an 2 hour time difference between Brisbane and Perth
The best day to arrive at Brisbane is Saturday and it would be best to avoid Wednesday, as prices are on average 97.5% higher than on Saturday. (Average prices, based on 312860 datapoints.)
We have a lot more statistics for flights QF 939 and between Brisbane and Perth.