Boeing B-52D Stratofortress
Design work for what would become the B-52 Stratofortress began in 1945. After several major design changes, the first of the eight-engined bombers took to the air on October 2, 1952. The first of the eight major production variants of the B-52 were built in 1954, with production continuing through 1963. The fourth model of the B-52 built, the B-52D was the second most produced version of the Stratofortress. Delivery of the “D” models began in 1956 with a total of 170 built.
As they were first built, the "D" model was virtually identical to earlier models of the aircraft except that it lacked the reconnaissance ability of earlier B-52s and was intended purely as a bomber. In 1965, modification of B-52D aircraft began to increase their conventional bomb load. The "Big Belly" modifications resulted in the ability to carry a total 108 conventional bombs both internally and externally. This means that one aircraft could carry 54,000 pounds of bombs, roughly the equivalent of nine World War Two B-17s. B-52s dropped thousands of tons of bombs on targets in Vietnam, becoming the symbol of American strategic air power during that war.