Flight Haneda Airport departs from Tokyo Haneda Airport at 22:55 and arrives at Singapore Changi Airport at 05:20.
The flighttime is about 7h 25m. The distance travelled ("as the bird flies"): 4314 Km. So the average speed is roughly 582 Km.
There is an 1 hour time difference between Tokyo and Singapore
The best day to arrive at Tokyo is Sunday and it would be best to avoid Saturday, as prices are on average 93.97% higher than on Sunday. (Average prices, based on 613509 datapoints.)
We have a lot more statistics for flights SQ 635 and between Tokyo and Singapore.
