In June 1943, preparations began for the operational use of atomic bombs. Although not as suitable for the atomic mission as the British Avro Lancaster with its cavernous bomb bay, Major General Leslie R. Groves, Jr., the director of the Manhattan Project, and General Henry H. Arnold, the Chief of United States Army Air Forces (USAAF), wanted to use an American plane, if this was at all possible, so the Boeing B-29 Superfortress was chosen, even though it required substantial modification. The modification project was codenamed Silverplate, but this codename eventually came to identify the training and operational aspects of the program as well.