The Stearman Model 4 is an open cockpit, 3 place biplane of beautiful proportion. Introduced in 1929 as a high performance sport biplane, the model 4 was quite flexible and adaptable to many business and commercial service uses. The 4D was the first certified airplane with the new Pratt & Whitney Wasp Junior engine of 300 hp. (R985) The first example of the model 4D was purchased by Pratt & Whitney for test and promotion of their new powerplant. Pratt flew the Stearman on an extensive air tour to acquaint prospective engine buyers and aircraft manufacturers with their new 300 h.p. engine.

Aircraft equiped with the Pratt & Whitney Wasp SC-1 engine of 420/450 hp were called 4E. Those designated 4C were equipped with a Wright J-6-9 Engine, and the 4D with the Wasp Jr of 300 h.p.. We can go on and seperate these biplanes into other categories..

Aircraft used for the flying of mail and cargo were called "Sr. Speedmail," or according to engine type 4CM, 4DM, or 4EM. Stearman Model 4's enjoyed by the sportsman pilot of the day were called "Jr. Speedmails," 4C, 4D, or 4E. Western Air Express used the Model 4D on its western mail routes, American Airways flew them between Atlanta and Chicago, Texaco Oil added a model 4, known as the Texaco 14, to their growing fleet of aircraft and Standard Oil owned 3 Model 4E's.