As Western wildfires burn bigger and more intensely this summer, one of the most effective tools in the firefighting arsenal is headed for retirement. The fleet of slurry bombers used to drop fire retardant has dwindled from 44 in 2004 to 17 this year, and by 2012, the big planes that rumble across Western skies during fire season will begin to be phased out because they are old and costly to maintain. Until funding for a new fleet of big tankers is found, the U.S. Forest Service will rely on heavy helicopters and single-engine air tankers, known as SEATS, to battle blazes in hard-to-reach places. Dry conditions in Western forests have made once unthinkable wildfires a possibility, said Jim Hubbard, the Forest Service's deputy chief for state and private forestry. 'That poses a real risk,' he added. The federal government is still hammering out how to fund the $2.5 billion it will take to replace the tankers -- aircraft that firefighters say are the best first strike against a wildfire. In the meantime, Colorado fire managers are lining up the single-engine planes to provide the initial attack on fires, said Sergio Lopes, the Colorado State Forest Service's aviation manager. The federal Bureau of Land Management also has two SEATS available to Colorado. If there are competing large fires in Western states, there could be a significant wait for available SEATs. Since 1988, the number of forest fires of 1,000 acres or more has quadrupled, the typical fire burns six times more land and the fire season is 78 days longer, according to Jeff Jahnke, director of the Colorado State Forest Service. If the worst happens -- multiple fires raging out of control in numerous Western states -- a fleet that relies mostly on heavy helicopters and SEATs would be able to handle it, Hubbard said. But Colorado state Sen. Dan Gibbs, a wildland firefighter who has fought fires in Colorado and California, would rather not risk it. 'They (big tankers) are like tools in the toolbox, and it's really important to have them all, depending on what the fire does,' said Gibbs. 'We need a broad range of tools that the state should be able to utilize if need be.' The dwindling number of big tankers, which can fly longer distances and carry more slurry to remote fires than SEATS, is worrisome for the 2010 season because conditions in the West are drier than normal and the potential for wildfire is higher. In 2002, there were two fatal tanker accidents in the nation, including one near Estes Park. In 2004, safety concerns grounded about half the fleet. The remaining planes move from fire to fire in the West as they are needed. 'They are aging, military-surplus aircraft, in some cases 50-plus years old,' said Hubbard. 'In 2012, we start losing (more) when we start rotating some out of service.' The Forest Service estimates it will take $2.5 billion to replace the leased fleet of heavy air tankers, which cost up to $75 million each. The Forest Service must buy the planes because they can't be leased from manufacturers at a reasonable cost, according to an audit of the purchase proposal by the Department of Agriculture last summer. 'I hope Congress would take this seriously and not wait for another large air tanker to go down, but look at the safety of pilots and communities,' Gibbs said. 'These huge tankers carry a tremendous amount of fire retardant and can do wonders for slowing down or containing fires, which protects communities and vital resources.' 