Aerial firefighting is the use of aircraft and other aerial resources to combat wildfires. The types of aircraft used include fixed-wing aircraft and helicopters. Smokejumpers and rappellers are also classified as aerial firefighters, delivered to the fire by parachute from a variety of fixed-wing aircraft, or rappelling from helicopters. Chemicals used to fight fires may include water, water enhancers such as foams and gels, and specially formulated fire retardants. Airtankers or water bombers are fixed-wing aircraft fitted with tanks that can be filled on the ground at an air tanker base or, in the case of flying boats and amphibious aircraft, by skimming water from lakes, reservoirs, or large rivers. Source: Wikipedia

In September 1999 I was able to visit the Air Tanker Base in Redding, California. Most of the aircraft in this set were operated by Aero Union, a specialist for aerial firefighting. Aero Union was also known for training crews in aerial firefighting and making custom designed fire fighting systems tailored to specific aircraft requirements. After controversies regarding the safety of their planes the U.S. Forest Service canceled its contract and the company was forced to shut down operations.  

All shots were originally taken on Ektachrome Film and later digitized.