Lockheed C-121 Constellation

The Lockheed C-121 Constellation is the military transport version of the Lockheed Constellation airliner, and 332 were built for the United States Air Force and United States Navy for a range of purposes, including several airborne early warning versions. Lockheed's first military Constellation, the C-69, had been troubled by its Wright R-3350 engines, so the post-war C-121 grew from the more economical L-749. In 1948 the Air Force ordered ten L-749A aircraft as the C-121A, with a reinforced floor and a large aft loading door, while the Navy ordered two radar versions. The C-121A was often fitted with 44 seats and a five-man crew, and later aircraft served with the Air National Guard and with smaller civilian operators until 1993.