Before and after World War II, planes used to spray crops were either civilian or military aircraft modified and equipped to apply liquid or dry materials. One of the most familiar was the open-cockpit Stearman biplane.
In the mid-1930s, the Army Air Service adopted the Stearman aircraft as its primary trainer. More than 10,000 were built before production shut down around 1943. In 1946, after the end of WWII, thousands of Stearman biplanes became available on the surplus market. Many of the planes were in like-new condition. Crop dusting companies began snapping them up at prices ranging from $250 to $875 per plane.
Modifications were required to convert the Stearman from a military trainer to a crop dusting plane, yet few commercial firms existed that could perform such work. Several companies stepped into the breach to specialize in such conversions. These firms also began to install dispensing equipment on a custom basis, which meant for the first time that agricultural flying companies could obtain dusting and liquid spraying equipment for their newly acquired aircraft. This development contributed significantly to the growth of agricultural aviation.
Stearmans became a favorite of many aerial applicators because they were affordable and easy to fly. It wasn’t uncommon for aerial application operations to have several Stearman planes in their ag fleet.