Air Tankers, Scoopers and Helicopters: How Firefighting Aircraft Really Work

A large air tanker laying a red line across a ridge is the image most people have of fighting a wildfire. Aircraft are a vital part of it, but they rarely put a fire out. Their job is to slow the fire down so crews on the ground can get ahead of it.

The main types of firefighting aircraft

Air tankers

Fixed-wing aircraft that load retardant at an airbase and drop it on the fire. They come in a wide range of sizes:

• Single-engine air tankers (SEATs) carry up to about 800 gallons. They're quick to reload and can work from small airstrips close to the fire.
• Large air tankers, often converted airliners or military transports, carry roughly 2,000 to 5,000 gallons.
• Very large air tankers, such as converted DC-10s, carry around 9,000 gallons and can lay a line more than a mile long.

Scoopers

Amphibious aircraft such as the Canadair CL-415 and its successor, the DHC-515, skim across a lake or reservoir to refill their tanks — about 1,600 gallons — in seconds without landing. Near water, they can make many drops an hour, which is why they're the workhorse in Canada and around the Mediterranean.

Helicopters

Helicopters drop water from a slung bucket or an internal tank, and the largest can carry over 2,000 gallons. They're more precise than air tankers and can refill from ponds, rivers and even swimming pools close to the fire. They also ferry crews into remote terrain and hoist injured people out.

The aircraft you don't notice

Above the tankers, a small air attack plane circles high over the fire. An air tactical supervisor in it coordinates every aircraft in the sky and talks to commanders on the ground. A lead plane often flies the drop path ahead of large tankers to mark the line and check for hazards. Other aircraft map the fire with infrared at night — the source of the perimeter maps you see in the morning.

Retardant vs. water

Water cools and wets fuel, but it evaporates quickly. Long-term fire retardant — the red stuff — is mostly water mixed with fertiliser-type salts. Those salts change how vegetation burns, so the treated strip keeps slowing the fire even after the water has dried. The red dye is only there so pilots can see where the last drop landed.

That's why retardant is usually dropped ahead of a fire, not on top of it: it builds a barrier the fire runs into. Water and gel drops, by contrast, are used directly on flames and hot spots.

Why aircraft don't put fires out

A retardant line slows a fire, but it can't stop one on its own — flames and embers can cross it, especially in strong wind. The fire is only held when ground crews build a control line down to bare soil, and only out when crews have cooled every hot spot near the edge. Our explainer on containment covers how that works. Air drops buy crews the time to do it.

When aircraft can't fly

• Strong wind. High winds make low-level flying dangerous and scatter drops before they reach the ground. On the worst wind-driven days — exactly when people most want to see aircraft — they may be grounded.
• Smoke. Heavy smoke hides terrain and power lines. Pilots need to see what they're flying into.
• Darkness. Fixed-wing tankers don't drop at night. Some agencies fly helicopters at night using night-vision goggles, but it's limited to certain areas and conditions.
• Drones. Any unauthorised drone near a fire forces aircraft to stop flying until it's gone, because a collision at low altitude could bring an aircraft down. Wildfires usually have temporary flight restrictions in place.

What aircraft overhead mean for you

Aircraft working a fire near you don't by themselves mean you're safe — or that you're in danger. They're often there because the fire is threatening homes and they're the fastest resource available. Follow your official evacuation level rather than reading the sky, and keep roads clear for fire engines. Don't stop on roads or park on road shoulders to watch drops.

To follow a fire's progress while aircraft work on it, open it on FireRadar's map to see its size, containment, perimeter and the latest satellite hotspots in one place.