The United States Navy Bureau of Aeronautics (BuAer) maintained record copies of engineering drawings for aviation equipment operated by the Navy and microfilm copies of these drawings were created by the Drawings and Microfilm Section of BuAer's Maintenance Division for the use of the Navy. In the mid 1980s, a portion of this drawing collection was loaned to the National Air and Space Museum (NASM) for processing by NASM personnel. In 1991, positive reference copies of microfilm, comprising some 3000 rolls, were loaned to NASM to assist in the processing of the hardcopy drawings and with the understanding that, should funding be available, NASM would duplicate the microfilm for its own collection as a "second security copy." The completion of the Archives II complex in College Park, MD in the 1990s allotted sufficient storage space to NARA's Cartographic and Architectural Branch for the RG72 drawing collection to be housed directly under NARA custody. As a result, NARA recalled its loan of the material, including the microfilm collection. The drawings were returned in 1994, but NARA granted an extension of the microfilm loan to allow NASM to duplicate portions of the collection which were relevant to NASM's artifact collection. The resulting 776 rolls of diazo 35mm film duplicates portions of microfilm contained in NARA RG72 and includes some records of the Drawings and Microfilm Section and Publications Section of BuAer's Maintenance Division.