The first operational airtanker was developed in Willows, by the Willows Flying Service, in 1955, at the request of the Fire Control Officer for the Mendocino National Forest (MNF). A Boeing Stearman 75 "Caydet" Agricultural Aircraft was modified with a 170-gallon tank at the Willows airport. This Aircraft, N75081, became the first registered free fall airtanker in the history of aviation. The first air drop was made on the Mendenhall Fire on August 12, 1955, on the MNF.

In 1956, seven agricultural aircraft were modified and formed the first operational airtanker squadron in the United States. Piloted by local aviators, this squadron operated out of the Willows Airport fighting wildfires throughout California. Initially, plain water was used as the fire suppressant. However, it was soon discovered that most of the water evaporated before reaching the fire. The practice was adopted of adding chemicals to the water to inhibit evaporation. Borate was one of the first chemicals used, hence the derivation of the term borate bomber.

In 1959, heavy airtankers, capable of carrying 2,000 gallons of fire retardant, were providing an effective tool in controlling wildfires. Today, the use of Single Engine Airtankers (SEATs) and Large Airtankers have become a staple for wildland fire suppression.

Content used with permission from the Early Aviators website.