 While various maintenance writeups had occurred and been cleared in accordance with existing maintenance procedures, in no case were both the captain's and first officer's altimeters reported malfunctioning at the same time.The flight's captain, 45-year-old Charles L. Cochran, had accumulated 12,895 hours of flight time, including 1,390 hours in the Convair 880.The first officer, 33-year-old Robert P. Moyers, had approximately 2,647 hours of flight time, including 447 in the Convair 880.