Flight Taipei Songshan Airport departs from Taipei Taipei Songshan Airport at 14:20 and arrives at Tokyo Haneda Airport at 18:45.
The flighttime is about 4h 25m. The distance travelled ("as the bird flies"): 2157 Km. So the average speed is roughly 488 Km.
The best day to arrive at Taipei is Saturday and it would be best to avoid Friday, as prices are on average 125.39% higher than on Saturday. (Average prices, based on 1707022 datapoints.)
We have a lot more statistics for flights JL 98 and between Taipei and Tokyo.