VASP Flight 168 departed S?o Paulo for a flight to Fortaleza, with an intermediate stop at Rio de Janeiro (GIG). The first leg of the flight was uneventful. As the flight approached Fortaleza, the crew were cleared to descend from their cruising altitude of FL330 to FL50 (5000 feet). In night-time conditions with the bright lights of the city in front, the captain descended below 5000 feet. Despite two altitude alert system warnings and the co-pilot’s warning of the mountains ahead, the captain continued to descend below the minimum descend altitude. The Boeing then struck a wooded mountainside at 1950 feet. Human Factor: It contributed to the extent that during the descent the Commander concentrated his attention on the illuminated city, disconnecting himself from other sensory impulses, such as observation of distance and altitude. Material Factor: Did not contribute. Operational Factor: Contributed for the reasons below: – Poor planning for the descent. – Non-observance of air traffic rules (non-compliance with control instructions, non-observance of the minimum safety altitude and non-maintenance of the speed foreseen for terminal flight below 10,000 feet). Therefore, serious flight indiscipline. – lack of cabin discipline. – Non-compliance with company operating standards.