Flight Haneda Airport departs from Tokyo Haneda Airport at 22:55 and arrives at Singapore Changi Airport at 05:25.
The flighttime is about 7h 30m. The distance travelled ("as the bird flies"): 4314 Km. So the average speed is roughly 575 Km.
There is an 1 hour time difference between Tokyo and Singapore
The best day to arrive at Tokyo is Monday and it would be best to avoid Friday, as prices are on average 226.85% higher than on Monday. (Average prices, based on 654795 datapoints.)
We have a lot more statistics for flights NH 6251 and between Tokyo and Singapore.
