An air tanker is a fixed-wing aircraft that is used to drop either water or a fire retardant on or in the path of a wildfire.
The size of air tankers varies widely from small single-engine propeller aircraft to large passenger jets.
Most air tankers are aircraft converted from other uses for firefighting. There are a handful of aircraft that were specifically designed for use as an air tanker, most notably the CL-215 and CL-415 by the Bombardier company of Canada.
The first air tankers were small single engine bi-planes based on agricultural aircraft used for spraying crops. The first use of air tankers on a fire occurred in 1955 on the Mendocino National Forest, located in Northern California.
Within a few years larger aircraft were being used. Many of the air tankers in use during the 1960s through the 1980s were converted WW2 bombers. As the airlines converted to jet aircraft in the 1960s large prop driven airliners became available and many were converted into air tankers. Naval anti-submarine aircraft and military cargo planes were also popular for conversions.
Due to the costs and specialized skills required to operate and maintain a fleet of aircraft most air tankers are operated by private aviation companies that contract their services to the government. A few nations place the operation of air tankers under the military.
In the United States air tankers are classified into 4 sizes, type 1 through type 4. Classification is based on tank capacity.
Air Tanker classification
Type 1 - 3000-5000 gallons, typically 4 engines.
Type 2 - 1800-2999 gallons, typically 2 or 4 engines.
Type 3 - 800-1799 gallons, 1 or 2 engines.
Type 4- 100-799 gallons, generally single engine.
Some additional terms are used to describe certain types of air tanker.
SEAT - Single Engine Air Tanker, these are generally small agricultural aircraft (crop dusters) and may meet Type 3 or Type 4 standards. They are often desirable in remote areas due to their ability to operate from short primitive landing strips.
VLAT - Very Large Air Tanker, this term has been applied to air tankers capable of carrying a considerably larger load of retardant than the minimum required to meet Type 1 standards. Currently the only aircraft meeting this definition are the DC-10 (11,600 gallons) and 747 (20,000 gallons). Aircraft such as the Russian Il-76 (11,574 gallons) would technically meet this definition, but are they are not being used in the United States.
LAT - Large Air Tanker, this term came about after the introduction of VLATs. It is typically applied to Type 1 and Type 2 air tankers.