The flight from London-Heathrow Airport to Milan-Linate Airport was normal until shortly after 18:38 hrs., when the aircraft reported its position over the Monte Ceneri NDB at FL170. A southerly alteration of course was then made to avoid a thunderstorm. At 18:52 hrs., after reporting southwest of Saronno at FL170, the aircraft was cleared to descend to 6,000 ft at the Linate NDB. But at 18:55 hrs the aircraft was still heading south because of thunderstorms over Linate and, when passing FL150, ATC requested that the descent should be stopped at FL130. At 18:58 hrs ATC recleared the aircraft to the Linate NDB at FL130, and then to descend in the Linate bolding pattern to 6,000 ft. At 19:00 hrs the captain reported at FL130 and said be would advice ATC when over the Linate beacon. At about 19:03 hrs he reported his position as over Voghera VOR and requested permission to continue to descend; ATC, however, withheld permission until the aircraft reached Linate. At this time, the Linate weather was reported as: visibility 20 kms, with thunderstorm, clouds 3/8 at 1,500 ft. and 6/8 CuNb at 3,000 ft. At 19:09 hrs the aircraft reported over Linate in thunderstorm conditions and requested permission to descend in the holding pattern; ATC cleared the descent to 6,000 ft. and, two minutes later, to 2,000 ft. At 19:17 hrs. the captain reported that he was having difficulty in receiving the beacon because of interference from the thunderstorm, but was inbound on the ILS. At 19:22 hrs. the aircraft reported at 2,000 ft. inbound, and the pilot added that he would report at the outer marker. This was the last message received from the aircraft, which flew into ground 2,000 ft. amsl, in line with the ILS localiser beam but 33 nm south of the airport. An examination of the wreckage showed that the aircraft had struck the ground in a level attitude with the undercarriage down. It then bounced and bit a sharp rise in the ground about 200 yards further on, causing a complete break-up of the aircraft structure. No evidence was found of any lightning strike and both pilots agreed that there was nothing wrong with the aircraft up to the time of the crash. Probable Cause: The Commission considers that the cause of the accident was a navigational error arising from the following omissions : (1) The failure to take the necessary bearings for a reliable determination of the aircraft’s position in view of the particularly unfavourable weather conditions . (2) The failure to make the fullest possible use of the services of the co-pilot.