In 1943 and 1944, 60 B-25s were chosen to be converted into advanced trainers. To create the AT-24A, B, C, and D models, all operational equipment was stripped from a selection of B-25C, D, G, and J variants. By 1948, the TB designation replaced the AT and all trainer Mitchells were renamed as the TB-25C, D, G, and J. Further conversions of B-25Js were carried out, bringing the total number of trainers to over 600. These aircraft were the last to serve in the USAF and were officially retired on May 21, 1960.