sentences:  A clearly determined TOC is predicated in planning along the intended route of flight far enough from the departure so that the aircraft is at altitude, on course, trimmed up in cruise flight.The variability of departure is now over and accurate tracking and monitoring of progress are beginning.Once past TOC (and by definition stabilized on course) a pilot can efficiently ascertain whether the wind and weather are "as forecast" and the groundspeed attained will allow for the safe completion of the flight "as planned" or within an acceptable margin for safety.