Line personnel who had serviced the airplane before takeoff reported seeing the second pilot load some items into the nose baggage compartment and lower, but not latch or lock, the left-side door. The airplane was then towed away from the fuel pit for start. Because the line crew had to leave briefly to marshal out another airplane, no witnesses could describe the exact sequence of events as the two pilots boarded the airplane for a 20-mile positioning flight to Long Beach. One reported, however, that the senior pilot, a 72-year-old ATP (who held ratings for several Boeings as well as the L-1011 and the MD-11 and was the founder and owner of the charter service operating the Citation), was in the left seat. The right-seat pilot, 49, had 1,700 hours and was qualified as a second pilot for Part 135 flights. Line personnel reported that the delay before engine start -- about 10 minutes -- was unusually long.