A National Guard Predator drone is flying over the vast Rim Fire near Yosemite park to send back real-time data to firefighters on its size and direction of the blaze in the longest such mission in California.
The unmanned drone launched Wednesday will be airborne for 22 hours.
"It will identify where fire activity is located and how it is moving, including locating and identifying spot fires which will improve the ability to protect life, property, and natural resources," the U.S. Forest Service said in a statement.
The 12-day-old Rim Fire has grown to 301 square miles, and officials said the fire was 30% contained as of Thursday morning.
''We continue to get line around this fire,'' said California fire spokesman Daniel Berlant. ''It's not nearly as active as it was last week.''
Fire officials estimate that it can be contained no sooner than Sept. 10.
The remotely piloted drone, which is the size of a small Cessna, has helped firefighters by shouldering the burden normally carried out by helicopters, which must be refueled every two hours.
The MQ-1 unmanned aircraft is from the California Air National Guard's 163rd Reconnaissance Wing from Riverside and is operating from Victorville Airport. It flew over mostly unpopulated areas on its 300-mile flight to the Rim Fire
''The drone is providing data directly back to the incident commander, allowing him to make quick decisions about which resources to deploy and where,'' Berlant said.
Officials were careful to point out the images are being used only to aid in the effort to contain the fire. Outside the fire area, it will be escorted by a manned aircraft.
In 2009 a NASA Predator equipped with an infrared imaging sensor helped the U.S. Forest Service assess damage from a fire in Angeles National Forest. In 2008, a drone capable of detecting hot spots helped firefighters assess movement of a series of wildfires stretching from Southern California's Lake Arrowhead to San Diego.