06/07/2021. Remarks by Johan Visschedijk: "The last of the Lockheed Altairs obtained by modifying an existing airframe was originally the Detroit-built DL-2 (NR8494). The DL-2 was of composite construction, featuring the famous Lockheed cantilever wooden wing and tail, but a metal fuselage that resulted from Lockheed's affiliation with the Detroit Aircraft Co. in 1929.

In early 1931 Lockheed modified the aircraft by adding an manually operated inward retracting landing gear and a more powerful 500 hp Pratt & Whitney SR-1340E nine-cylinder air-cooled radial engine. This aircraft was designated DL-2A Altair. Later in 1931, the USAAC bought this aircraft and designated it Y1C-23 and allotted the serial 32-232. Intended as a fast executive staff transport, the aircraft looked more like a fighter than a transport. It had room for one passenger and about 1,000 lb (454 kg) of cargo could be stowed in a small compartment.

After initial service testing at Wright Field, Dayton, Ohio, the Y1C-23 was assigned to Bolling Field, Washington, D.C., as a staff transport for use by the Assistant Secretary of War, the Chief of the Air Corps, and other key officers. The aircraft was re-designated as C-23 when the Y1 prefix was dropped in 1933. During its seven-year military flying career this aircraft had minor modifications, including a tail wheel replacing the original tail skid, as well as an adjustable pitch propeller. It survived at least five wheels-up landings before being assigned as a ground instructional airframe to Chanute Field, Illinois, after having flown a total of 1,075 hours. It was finally scrapped at the Middletown Air Depot, Pennsylvania, in June 1942.