sentences:  The aircraft immediately became uncontrollable and crashed.According to an investigation by both the Argentine and Uruguayan Air Forces, the pitot tube—the primary instrument for measuring aircraft airspeeds—froze when the aircraft passed through a high cumulonimbus cloud, blocking the instrument and causing it to give a false reading.Compounding this problem was the absence of the alarm designed to report such a malfunction (raising serious questions about inspection irregularities by the Argentine Air Force).