A less radical design by Dr. John E. Younger featured all-metal construction; the aircraft was built as an all-metal, low-wing, retractable gear, twin engine transport with a triple vertical tail supporting a dual (biplane arrangement) horizontal stabilizer.
Following a 1938 incident, the XC-12 was modified at Glendale, California: The forward slanting eight-piece windshield was modified to a four piece that slanted rearward, and the passenger windows were squared off to look more like a Douglas DC-3.