The Standard J-1 is a two-seat primary trainer developed from the earlier Sloan and Standard H-series aircraft designed by Charles Healey Day. When the U.S. entered WW I, the Army ordered the aircraft (then known as the SJ) produced as a supplement to the Curtiss Jenny then in production. At about the same time, Standard introduced an advanced version of the SJ called the JR. The Army bought only six of the JR-series aircraft, but some of the JR's features were incorporated into SJ production aircraft; the resulting version became known as the J-1.