The Forest Service and the Interior Department are terminating contracts with private companies for use of the former military aircraft that had been powerful weapons against wildfires.
The government said Monday other aircraft would do the jobs that the air tankers had done. But Western officials, worried about fire danger in a region plagued by continuous drought, said the loss of the planes compounds their problems.
Forest Service Chief Dale Bosworth said the big planes had to be taken out of service.
"Safety is a core value of the firefighting community, and it is nonnegotiable," he said. The planes pose an unacceptable risk to flyers, firefighters on the ground, and communities near fires, he said.
Between 1994 and 2002, three planes crashed, killing seven crew members. After two of the planes went down in 2002, the Forest Service grounded the contracted tanker fleet. The planes were returned to service after a new inspection system was developed. But last month, the National Transportation Safety Board said the safety and airworthiness of the fleet still could not be assured.
The agency said information on the stresses that the planes underwent in fighting fires was incomplete, and there were gaps in maintenance and inspection records dating back to the planes' military use. The planes' average age is 48 years, yet some are as old as 60 years.
The aircraft were capable of dumping 1,700 to 2,500 gallons of water a minute, and were used primarily in initial attacks on fires and for protecting buildings when fires advanced to urban areas, said Dan Jiron, a Forest Service spokesman.
However, the fire could be fought with other aircraft, including water-carrying helicopters and fixed-wing planes akin to cropdusters, Jiron said. These aircraft can make much more accurate attacks, he said.
Also, the smaller aircraft can make repeat trips from water sources, said Rose Davis, a spokeswoman for the National Interagency Fire Center in Boise, Idaho. "A helicopter can load and return 1,500 gallons four to five times as fast as an air tanker," she said.
In any case, most of the effort to fight wildfires is not done from the air, Davis said. "Fires are put out on the ground," she said. "Air support means support."
Much of the West is gripped by drought, with some of the region affected by it for the last four years, Davis said.
Firefighters have enough resources for the initial attack and can add helicopters and small airplanes later if needed, she said.
Jiron said that firefighters also can activate 8 military C-130s equipped to dump water on fires.
Despite the government's confidence that firefighters can cope without the aircraft tankers, some officials in the West remained worried and were examining alternatives.
"We're not panicking, but it's a problem," said Steven Robinson, an adviser to Nevada Gov. Kenny Guinn.
Robinson said the state would look to its National Guard Chinook helicopters and utilize prison inmate crews to help fight the fires.