If the planned and actual airspeed are both 160 kt, and the pilot notices that the planned timings overhead the chosen waypoints are not corresponding to the actual timings, and that the aircraft is getting behind the timings, the main reason for the deviation from the planned timings is likely to be a headwind or tailwind component.

Wind is a major factor that affects the progress of a flight, and it can cause a deviation from the planned timings. A headwind component will slow down the aircraft and increase the flight time, while a tailwind component will speed up the aircraft and decrease the flight time.

The pilot should check the current wind conditions and make the necessary adjustments to the flight plan, such as adjusting the planned ground speed, fuel consumption, and arrival time. If the wind conditions are significantly different from those forecasted, the pilot may also consider diverting to an alternate airport or requesting a new clearance from ATC.