The first airframe built was the Western Museum of Flight's JB-1 mancarrying glider. The JB-1 was used to explore the design's flight characteristics. This piloted version was lifted aloft as a glider by means of a tow aircraft.
Tow hitches are visible at the tips of the two bomb containers.
The center section was fabricated of formed and welded magnesium alloy plate. The wing panels were made of riveted and spot-welded aluminum alloy sheet with magnesium wingtips. The pilot's cockpit was located in the space that would be used for the jet engine installations in the unmanned JB-1A powered model. In 1944, Northrop test pilot Harry Crosby made the initial glider flights out of Muroc Dry Lake, using airplane tows to get airborne. Following the successful glider flights, the second model JB-1A was equipped with a pair of General Electric Type B1 turbojet engines replacing the pilot.