On Aug. 6, 1945, the United States dropped an atomic bomb on the Japanese city of Hiroshima. It was the first time a nuclear weapon had been used in warfare. There were three strike planes that flew over Hiroshima that day: the Enola Gay, which carried the bomb, and two observation planes, the Great Artiste and the Necessary Evil. Russell Gackenbach was a second lieutenant in the U.S. Army Air Corps and a navigator on the mission. Today, the 95-year-old is the only surviving crew member of those three planes.