Groundspeed
315kts
Distance 475nm
ATD (Actual Time Departure) 10:00
Initial time to B = 91 mins
ETA B = 11:31
Fix at 10:40 190 nm along track - 190 nm in 40 mins =
groundspeed 285 i.e. less than planned.
Distance to go 285
Time to original ETA of 11:31 = 51 mins
285 nm in 51 mins requires GS of 336kts.
Nearest answer 340kts