The Red Stuff: How Aerial Retardant Aircraft Fight Fire in the Early Season

Few images are more emblematic of western wildland firefighting than a low-flying air tanker trailing a plume of rust-red retardant across a hillside. These aircraft are among the most valuable and complex tools in the firefighting arsenal, and as fire seasons start earlier and fires burn more intensely, they are being called upon more frequently — and earlier — than ever before.

What Aerial Retardant Does

Aerial fire retardant — the distinctive red or pink liquid dropped from air tankers — is primarily composed of water mixed with a phosphate-based fertilizer compound called Phos-Chek. The fertilizer coating left on vegetation after the water evaporates slows combustion by raising the ignition temperature of fuels. Unlike water drops, which suppress active fire primarily through cooling, retardant works by chemically altering the fuel ahead of the fire, creating a line that can slow or stop spread long enough for ground crews to construct a fireline.

Retardant is not a fire extinguisher — a drop in the middle of an active flame front does little. Its power lies in strategic placement ahead of the fire, on the flanks or in the path of spread.

Types of Retardant Aircraft

The aerial firefighting fleet includes several distinct aircraft types, each suited for different conditions:

Single Engine Air Tankers (SEATs): Smaller, highly maneuverable agricultural-type planes carrying 800–1,200 gallons. Fast to load and redeploy, ideal for initial attack on smaller fires in accessible terrain.
Multi-Engine Air Tankers (MEATs/Large Air Tankers): Modified commercial airliners or cargo aircraft — including the legendary DC-10 and 747 "Supertankers" — capable of carrying 3,000–19,000 gallons per load. Used for large-scale drops on major incidents.
Very Large Air Tankers (VLATs): Boeing 747-based platforms capable of 19,000-gallon loads. Relatively rare but deployed on the most extreme incidents.
Helitankers: Helicopters equipped with fixed tanks or helibuckets for precision drops in areas fixed-wing aircraft cannot safely access.

Early Season Advantages

Early in fire season, aerial retardant is especially effective because fires tend to be smaller, terrain access is easier, and the relative humidity is higher than mid-summer — meaning drops hold longer before burning off. Fire managers and aviation coordinators work closely in the early season to maximize initial attack success: get enough aircraft on a fire within the first few hours, and the odds of keeping it small increase dramatically.

The NWCC prioritizes early aerial response for initial attack precisely because a fire caught at five acres is vastly cheaper and safer to suppress than one that escapes to 500 acres due to delayed resources.

Airtanker Base Infrastructure

To be effective, retardant aircraft must be stationed close to where fires are expected. The PNW operates several key airtanker bases: Redmond, Oregon is a major hub, along with bases at Missoula, Boise, and Yakima. These bases maintain rapid-reload capability with pre-mixed retardant and fueling infrastructure. Turnaround time from landing to re-loaded takeoff can be as little as 10–15 minutes for a SEAT.

Limitations and Challenges

Aerial retardant has real limitations. Aircraft cannot fly safely in smoke, at night, in high winds, or in terrain that doesn't allow safe drop runs. On days with extreme fire behavior — the kind that increasingly characterizes PNW summers — aircraft may be grounded precisely when they're needed most. Environmental restrictions also prohibit retardant drops within 300 feet of waterways to protect aquatic species.