When Jack Northrop set up the Northrop Corporation as a joint venture with the Douglas Aircraft Company in 1932, he set out to design two closely related single-engined aircraft as the new company's first products, a mailplane/record breaking aircraft, which was designated the Gamma and a passenger transport, the Delta.
The 1957 motion picture The Spirit of St. Louis featured an RAC DH-4 mailplane in flying sequences as well as Maj. Robertson (played by James Robertson, Jr.) and company Air Mail pilots Lindbergh (James Stewart) and Harlan A. "Bud" Gurney (Murray Hamilton) among its characters.
The MB-4 was designed to meet a June 1919 specification from the United States Post Office Department for a two- or three-engined mailplane, required to carry 1,500 lb (682 kg) of mail on a single engine.