Lockheed 8 Altair

When acquiring his Sirius, Charles Lindbergh had intimated that he might be interested in having retractable landing gear, with a result that the company designed an alternative wing to accept inward-retracting main landing gear units. Although this feature was not adopted by Lindbergh, it became available as a retrofit for Sirius aircraft, first flown on a company-owned Sirius 8A during September 1930. Redesignated Lockheed Altair 8D in this form, the aircraft was loaned to the US Army Air Corps during 1931 and in November of that year, with a new 336kW Pratt & Whitney R-1340-17 engine installed, was acquired by the USAAC under the designation Y1C-25. Four more aircraft were converted, two Sirius 8As becoming Altair 8D aircraft, the Detroit Aircraft DL-2 being redesignated Altair DL-2A and, most famous of all, one Sirius receiving the designation Sirius 8 Special. This last aircraft was later acquired by Sir Charles Kingsford Smith and, modified to Altair 8D configuration and named Lady Southern Cross, was used by this pilot, with P. G. Taylor as his navigator, to make the first crossing of the Pacific Ocean from Australia to the United States between 20 October and 4 November 1934.

In addition to the conversions, six Altairs were built as new, one of them an Altair DL-2A built by Detroit Aircraft and powered by a 481kW Wright R-1820E Cyclone which was acquired by the US Navy under the designation XRO-1.