In 1935 the school was transformed into the Military Aeronautics division (Aeronáutica Militar,) and five units were created as well as several airbases. Typical aircraft of the thirties and forties were European types like the Potez XXV A. 2 TOE, the SPAD S. VII and S. XIII, the de Havilland DH 82A, and the IMAM Ro. 37; but this era also saw the transition to aircraft of American pedigree. Beech AT-11 and Douglas C-47 transports, Waco JHD and NAA Texan trainers, and NAA B-25J bombers were used in this period. The arrival of F-51 Mustangs in the early 50s notably enhanced the capabilities of the air force. There were now nine Aviation Groups and the Military Aeronautics division was officially renamed the Military Air Force (Fuerza Aérea Militar) on 4 December 1952. This change in nomenclature was important because it signified the independence of the branch from the army command structure. The new force was reorganized into three commands (tactical, training, and material) and a brigade structure was implemented along with a fully staffed headquarters.