At the time of this photo smoke billowed 20000 feet above Hiroshima while smoke from the burst of the first atomic bomb had speed over 10000 feet on the target at the base of the rising column. August 5 1945 two planes of the 509th composite group, part of the 313th wing of the 20th Air Force, Participated in this mission, one to carry the bomb, the other to act as escort. US air force.