Two versions of the same basic design were built for the United States Air Force, one made largely of wood with a fixed landing gear, and one with a metal skin and retractable landing gear, designated Y1C-25 and Y1C-23, respectively.

[4] In 1931, György Endresz and Sándor Magyar made a successful US–Hungary transatlantic flight with a Lockheed Sirius 8A aircraft named "Justice for Hungary".

[5] In 1933, the Lindberghs set out again with their Sirius, now upgraded with a more powerful engine, a new directional gyro, and an artificial horizon.

[6] While at a refueling stop in Angmagssalik, Greenland, the Inuit of the area gave the Sirius a nickname, "Tingmissartoq" or "one who flies like a bird".

They continued on their flight and made many stops in Europe, Russia, then south to Africa, back across the southern Atlantic to Brazil and back over New York City at the end of 1933, after 30,000 miles and 21 countries; droves of people turned out to greet them as they landed.