The debris from the pitot probe was not recovered, so it was not possible to determine the source of the material that obstructed the co-pilot’s pitot probe. Recorded data showed that the calculated airspeed on the co-pilot’s system remained at 0 kt throughout the event and so it is likely that the system was significantly blocked.The engineering checks carried out on the aircraft before and during the parked period all recorded that pitot covers were fitted. It was not possible to determine when the pitot blockage occurred.