Flight Taoyuan International Airport departs from Taipei Taoyuan International Airport at 17:00 and arrives at Hong Kong Hong Kong International Airport at 19:05.
The flighttime is about 2h 05m. The distance travelled ("as the bird flies"): 826 Km. So the average speed is roughly 396 Km.
The best day to arrive at Taipei is Thursday and it would be best to avoid Tuesday, as prices are on average 12.35% higher than on Thursday. (Average prices, based on 4174097 datapoints.)
We have a lot more statistics for flights CX 421 and between Taipei and Hong Kong.