"We are confident the unsurpassed firefighting ability of the Global SuperTanker will be a tremendous asset for CAL FIRE and its team on the ground as they suppress the Ponderosa Fire".
Thousands of people have been driven from their homes in OR and hundreds in California, where a blaze burned 10 homes and threatened 500 more near a hard-hit community and another kept a popular road to Yosemite National Park closed.
The fire could make air unhealthy to breathe in parts of Los Angeles, the nation's second-largest city, and nearby suburbs, the South Coast Air Quality Management District said in an advisory.
Structure defense remains a priority and firefighters continue to establish containment lines, Cal Fire said.
The fire department says approximately 50 homes are being threatened. It now hosts non-nuclear experiments and safety training.
"It's risky work where they're at", said Capt. Joe Chavez, with the California Department of Forestry and Fire Protection.
The fire has burned 10 residences and 20 outbuildings and is threatening 1,300 structures, including 500 homes, Cal Fire reported Thursday morning.
He added it was hoped firefighters could make good progress Wednesday on the Ponderosa Fire so "we won't have to increase anymore warnings or orders and hopefully at some point we can start talking about repopulation and getting folks back in their homes".
The blaze that began Tuesday near the town of Oroville is among a series of wildfires burning across the U.S. West, including in and around California's Yosemite National Park.
He says aircraft are attacking the flames that are chewing through sagebrush and cheatgrass in temperatures expected to reach triple digits.
The converted Boeing 747-400, which is based in Colorado Springs, is dropping retardant on the Ponderosa fire that's burning 10 miles east of Lake Oroville.
Authorities on Wednesday arrested a man suspected of starting an illegal campfire believed to have ignited the blaze that has also damaged five homes.