LAT

A large air tanker, or LAT, is a fixed-wing aircraft modified to carry and deliver water or fire retardant over active wildfires. These are utility workhorses operated by government agencies and private contractors, typically able to hold 3,000 to 19,500 gallons of liquid depending on the airframe. They fly low and slow over burning terrain, dropping their load in patterns designed to slow fire spread or protect structures and personnel on the ground.

The aircraft are retrofitted versions of aging cargo or military transport planes. Common frames include Lockheed C-130 Hercules variants, Bombardier CL-415 amphibians, and purpose-built or heavily modified Douglas DC-6 and Conair Turbo Firecat models. Each has different tank configurations, drop systems, and operating economics. The CL-415 and amphibious variants can scoop water directly from lakes or rivers, while others rely on ground crews to load at established bases.

Retardant versus Water

LATs typically carry one of two liquids. Fire retardant is a slurry containing ammonium sulfate or ammonium polyphosphate mixed with water, clay, and a colorant (usually red or orange); it clings to vegetation and slows combustion chemistry. Plain water is cheaper and denser, giving greater weight per gallon, but offers no lasting protection. Retardant operations require more pre-positioning and coordination because the material is expensive and only effective when applied ahead of the fire's path.

Performance depends heavily on weather and terrain. Strong winds can push the drop pattern sideways or cause uneven coverage. Smoke obscures targets. Steep canyons and mountain passes limit approach angles and increase pilot workload and risk. Turbulence and ash ingestion present mechanical hazards. Most LAT operations occur in daylight because night flying over mountains at low altitude with uncertain ground visibility is extremely dangerous.

LAT deployment is coordinated through incident command systems during large fires. Dispatch decisions rest on cost per drop, fire behavior, resource availability, and probability of impact on structures or suppression efforts. A single LAT sortie costs thousands of dollars; effectiveness is measured in containment miles and lives protected, not in acres burned per drop. The aircraft are most valuable in the initial attack phase when fires are small and when protecting communities at the wildland-urban interface.