Flight Changi Airport departs from Singapore Changi Airport at 13:05 and arrives at Hong Kong Hong Kong International Airport at 17:05.
The flighttime is about 4h 00m. The distance travelled ("as the bird flies"): 1322 Km. So the average speed is roughly 330 Km.
The best day to arrive at Singapore is Saturday and it would be best to avoid Tuesday, as prices are on average 180.57% higher than on Saturday. (Average prices, based on 2222528 datapoints.)
We have a lot more statistics for flights AC 6303 and between Singapore and Hong Kong.