The Stearman XA-21 (Model X-100) was a competitor in a United States Army Air Corps competition for a twin engined attack aircraft.
The X-100, designated XA-21 following purchase by the Army Air Corps, was a twin engined high-winged monoplane of all-metal construction.
Its initial design featured an unusual step less cockpit arrangement, much like those on most German World War II bombers designed during the war years from the He 111P onwards, with a streamlined, well-framed greenhouse canopy enclosing both the pilot and bombardier stations.
The XA-21 was first tested with the streamlined cockpit, but this configuration was found to restrict the pilot’s forward vision, and the aircraft was rebuilt with a conventional stepped nose and cockpit structure.
Although this change in the cockpit did not significantly affect performance, the XA-21 was not ordered into production.