LOS ANGELES — The U.S. Forest Service said Thursday it will permit agency helicopters to attack wildfires at night in Southern California, a significant policy shift that follows complaints about a 2009 blaze that became the largest in Los Angeles County history.

The night-flying program will begin modestly by next year with the use of a single helicopter, stationed in Angeles National Forest, where the 2009 Station Fire killed two firefighters, destroyed 89 homes and blackened 250 square miles.

After the huge blaze, the Forest Service was sharply criticized by residents who lost homes. Politicians clamored for changes, and government records opened questions about whether firefighting aircraft could have been ordered and deployed more quickly, including at night.

Tom Harbour, director of fire and aviation management for the Forest Service, said political pressure did not prompt the shift, which should have the helicopter in place no later than next June.

"This is a professional decision made by a professional organization after careful analysis and study of the pros and cons, the costs and the benefits," Harbour told The Associated Press in an interview.

The agency has long been reluctant to fly in darkness in rugged national forests for safety reasons. The Forest Service experimented with night flying against wildfires in the 1970s and early 1980s but abandoned it after a helicopter collision.

"There certainly are additional risks and additional expenses," said Harbour, adding that the program would be funded initially with $2 million that would go toward training, staff and equipment, including night-flying goggles. The helicopter will be operated by a contractor.

Some critics have suggested water-dropping helicopters could have slowed or extinguished the Station Fire on its first night, before it grew into an inferno.

A 2009 Forest Service review found the fire raged out of control because it jumped into inaccessible terrain, not because the agency scaled back firefighters or aircraft attacking the flames.

A U.S. Government Accountability Office report revealed conflicting accounts of why an air tanker was not summoned in the early hours of the blaze, but it noted that firefighting decisions are made under heavy pressure with imperfect information, and it acknowledged investigators had only limited ability to second-guess firefighters.

"Even less clear is whether, and to what extent, different decisions might have changed the outcome of the fire," the GAO report concluded.

The decision to use the helicopter was first announced by Sen. Dianne Feinstein, D-Calif., and area Reps. Adam Schiff, a Democrat, and Howard "Buck" McKeon, a Republican.

"This is long overdue but a welcome policy change by the Forest Service," Feinstein said in a statement. "Attacking fires from the air at night can bolster firefighting efforts because temperatures are cooler, humidity is higher and Santa Ana winds die down. "

Last year the Forest Service announced an agreement with local firefighters that made it easier to get water-dumping helicopters into the air at night over the fire-prone Angeles National Forest. The deal eliminated a requirement that homes or other structures must be in immediate danger for foresters to request help from the county's night-flying helicopters.

Water- and retardant-dumping aircraft rarely extinguish wildfires. That job falls to ground crews. Embers, brush and grasses on the forest floor can continue to burn even after a water or retardant drop.

Harbour stressed that the expansion into night flying will not guarantee that every wildfire is extinguished promptly, in all circumstances. He said studies suggested that night flights could be effective in about 30 percent of the wildfires likely to be faced in the region.

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