The two jets flying low and loud over Salt Lake City’s Avenues neighborhood may not be the F-35 Utahns are used to hearing scream around the Salt Lake Valley, but they are from Hill Air Force Base, and they are on bombing runs, of sorts.

On Sunday, two large air tankers from the Forest Service facility at the base made multiple drops of red fire retardant on the Bonneville Fire, a fire official told The Salt Lake Tribune.

The jets can carry thousands of gallons of fire retardant, the official said.

The red mixture seen dropping out of planes over wildfires can, according to the U.S. Forest Service, “alter the way fire burns, decreasing fire intensity and slowing the advance of a fire, even after the water the retardants originally contained has evaporated.”

The jets were also joined by two single-engine air tankers, knowns as SEATs, and a helicopter that appeared to be similar to one that initially began fighting the grass fire on Saturday afternoon.

On Sunday morning, fire officials said the Bonneville Fire — which started in the foothills behind the University of Utah on Saturday — had doubled in size overnight, growing to around 400 acres.

Watch a large air tanker drop from Hill Air Force Base drop fire retardant on the Bonneville Fire: