The Stearman XA-21 (Model X-100) was a competitor in a United States Army Air Corps competition for a twin-engined attack aircraft which (after redesigns) led to the Douglas A-20 Havoc, Martin A-22 Maryland and North American B-25 Mitchell.

The X-100, designated XA-21 following purchase by the Army Air Corps, was a twin-engined high-winged monoplane of all-metal construction.

[1] Its initial design featured an unusual "stepless 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.

[3] Although this change in the cockpit did not significantly affect performance, the XA-21 was not ordered into production.

[5] Data from Museum of the United States Air Force[4]General characteristics Performance Armament