Aerolineas Argentinas flight 670, a Douglas DC-4, crashed near Bolivar, Argentina, following an in-flight breakup, killing all 61 occupants. The Aerolineas Argentinas DC-4 took off from Buenos Aires-Ezeiza at 15:54 for a flight to San Carlos de Bariloche. The crew were cleared for an IFR flight outside airways with a minimum altitude of 1200 m to Neuquen and 2400 m from Neuquen to San Carlos de Bariloche. It was established that the aircraft flew at 100-150 m for a distance of 35-40 km, deviating 21 km from its intended route. It is assumed that the pilot tried to fly below an intense upper front. The DC-4 flew into the front at its most active part, climbed sharply. At about 2500 m the aircraft lost control and dove to the ground. It struck the ground at a 35deg descent angle, 25deg left bank and with a speed of over 400 km/h. PROBABLE CAUSE: “The aircraft disintegrated in flight due to breakage of parts of the left wing followed by the falling off of the tail section when the equipment was subjected to stresses above those envisaged by the manufacturer. This was brought about as a direct result of the pilot’s decision to attempt to cross a cold surface front under turbulent conditions of extreme severity. Contributing causes were: 1) The pilot’s recklessness in descending on a track well below the minimum safety flight altitude established for this type of operation.; 2) The absence in the flight plan of a forecast showing the intensity of the meteorological phenomena encountered; 3) Inadequate operational dispatch of the aircraft.”