Add another concern for the tanker plane pilots who barnstorm low over treacherous terrain, in vintage aircraft, to bomb fire retardant around raging mountain wildfires: Endangered species.

New U.S. Forest Service rules for the use of fire retardant in dozens of national forests seek to prevent the millions of gallons of fire retardant spread over the landscape every year from poisoning streams and killing off protected plants and fish.

Forest Service officials insist the new rules won't hinder firefighting. The company that operates almost half of the U.S. private fleet of large tanker planes agrees, for the most part.

"It is an increasing workload, there's no doubt about that," said Dan Snyder, president of Missoula, Mont.-based Neptune Aviation Services, which operates eight Lockheed P2V planes.

"It may reduce the speed at which they can affect the fire because they do need to take those few extra minutes to study the charts and plan on how they can put the retardant on the ground and still comply with the rules."