Piloting a firefighting aircraft is sweaty, tiring work, Mr. Mattiacci said. The conditions that increase fire risk — hot days, high wind, often mountainous areas — also make for turbulent flying conditions. The aircraft fly at low speeds, increasing the turbulence, he added.

“You get pulled up out of your seat and your head bangs against the roof,” he said. In the hot conditions, pilots must keep just hydrated enough not to have to use the bathroom, on flights that can last up to five hours, he said.

There’s also a risk of flying into the thick, blinding smoke that wildfires send up, he said. The aircraft flying low to the ground — sometimes as low as the height of treetops — meaning there’s a significant risk of flying into power lines, radio towers and buildings.

“When we lose all visual reference, it gets a bit scary,” he said.

The stronger the winds, the harder it is to get close to the fire, as winds push the smoke around and obstruct visibility.

The large air tankers in Australia drop retardant from an altitude of about 100 to 150 feet, he said, while smaller ones can fly even lower. The largest tankers — which can carry up to 9,400 gallons of fire retardant at a time, and have been used to fight the Southern California fires — drop from about 250 feet, according to the National Interagency Fire Center.

Mr. Mattiacci said that he often feels pressure as he looks down from the cockpit at homes and structures under threat, knowing his job is to help save them. And if the fire retardant doesn’t land where it’s needed, he added, during a fast-moving fire, “there might not be another chance.”