Jae C. Hong, File, Associated Press
FILE - In a Thursday, Sept. 17, 2009 file photo, a truck drives past burned trees in the Angeles National Forest near Los Angeles. A draft report obtained by The Associated Press discloses conflicting accounts of why an air tanker was not summoned in the early hours of the largest wildfire in Los Angeles County history. Critics have long said the Forest Service didn't bring in enough aircraft and firefighters to quickly snuff the 2009 Station Fire in the Angeles National Forest.

LOS ANGELES — A draft report discloses conflicting accounts of why an air tanker was not summoned in the early hours of what turned out to be the largest wildfire in Los Angeles County history, but the document obtained Friday by The Associated Press concludes it's not possible to know if different decisions would have extinguished the blaze.

The 2009 arson-caused Station Fire killed two firefighters, destroyed 89 homes and blackened 250 square miles on the edge of Los Angeles, and residents who were burned out have long complained the Forest Service allowed the flames to spread by failing to bring in enough firefighters and aircraft to do the job.

Government records released after the blaze opened questions about whether firefighting aircraft could have been ordered and deployed more quickly, including at night, and whether a tight federal budget drove firefighting decisions on the ground.

The 67-page draft U.S. Government Accountability Office report concludes the Forest Service needs to clear up foggy policies that could cause confusion when working with local firefighters, but it stops short of suggesting the Station Fire could have been stopped in its early hours.

"These decisions may be made with imperfect information and under severe time constraints, relying heavily on the professional judgment of those involved. It is not possible to know with certainty whether different decisions or actions would have resulted in a different outcome for the Station Fire," the agency concluded.

The report said the agency should "clarify ambiguous operational processes, and address broader issues regarding its use of assets to fight fires, thereby laying the groundwork for improvements to its management of future fires."

Early in the first evening of the fire, on Aug. 26, 2009, an air tanker was nearby that could have been diverted to the Station Fire, according to the document. But accounts of why that didn't happen differed.

Citing interviews, the report said the supervisor at the Station Fire did not summon the firefighting plane, in part because it was getting dark. But the pilot told investigators darkness was not an issue and "he believed there was ample time for the tanker to fly to the Station Fire, make its drop, and return to base before nightfall."

But the report also notes large air tankers, typically used to dump retardant or water along ridge lines, might have had problems in the steep canyons where the fire was burning. "The tankers would have had to fly high enough to be safe from the power lines and the drops from such heights would likely have been ineffective," the report states.

The Forest Service summoned several powerful firefighting airplanes in the early stages of the wildfire, then canceled and reordered them, causing a two-hour delay in their arrival on the second day of the fire, according to government records released after the blaze. Recordings of calls between fire managers and dispatchers released last year showed the difficulty of communication in the mountainous region, and the problem of deploying aircraft as multiple fires burned in the state.

But in part because of rest requirements for flight crews, "it appears unlikely that any federal air tankers could have arrived over the Station Fire sooner than they did," the report said.

A federal review in 2009 found the fire slipped out of control because it jumped into steep, inaccessible terrain, not because the Forest Service scaled back firefighters and aircraft attacking the flames.

"We are not constrained by cost. We want to get the fire out," Forest Service Fire and Aviation Management Director Tom Harbour said at a congressional hearing earlier this year, defending the agency's response in the early hours of the blaze.

Members of Congress asked the watchdog GAO to conduct a broad review of the fire in 2010.

Federal foresters have long discouraged night flying because of the risk of operating aircraft in darkness in rugged national forests, but the agency reached an agreement with local firefighters earlier this year that makes it easier to get water-dumping helicopters into the air at night over the fire-prone Angeles National Forest.

Critics have suggested that deploying waves of water-dropping helicopters could have slowed, or extinguished, the fire on its first night, before it raged out of control.

The agency has argued that there are scant cases where aircraft alone extinguish fires, since embers, brush and grasses on the forest floor can continue to burn even after a water or retardant drop.