The experimental NA-21 Dragon was North American's first venture into multiengine design. It was a high-altitude bomber armed with single .30-inch machine guns in each of five positions, including in a ball-type turret in the nose. The NA-21 could carry 10,000 pounds of bombs short distances or carry 2,200 pounds of bombs for 1,900 miles.
After a few small changes, the NA-21 was accepted for testing at Wright Field but orders did not follow. The Air Force bought the single NA-21 in 1939 and redesignated it the XB-21.