Air Force officials are expected to decide as soon as next month whether to go forward with an expansion of a bomber training area over the Northern Plains that would encompass an area larger than West Virginia.

Known as the Powder River Training Complex, the area includes portions of Wyoming, Montana and the Dakotas. It would be used by B-1 bombers based at Ellsworth Air Force Base in South Dakota and B-52 bombers at Minot Air Force Base in North Dakota.

Air Force officials say the expansion of the training airspace to about 28,000 square miles is needed to keep its force ready for combat. It also would save the military $23 million a year, by reducing the number of sorties now being sent to Utah and Nevada for exercises, officials said.

But the prospect of bombers roaring over rural communities 240 days a year has drawn resistance, with one Montana official referring to the proposal as a federal government "airspace grab."

Montana Department of Transportation Aeronautics Division Administrator Debbie Alke said she's been told by Air Force officials that a final environmental study of the proposal will be released next month.

Ellsworth spokesman Capt. Christopher Diaz said the study will be completed after the Air Force finishes consultations with interested parties. That would kick off a 30-day waiting period before the Secretary of the Air Force signs a final decision, officials said.

The Federal Aviation Administration also must approve the proposal.

A B-1B from Ellsworth crashed in August in southeastern Montana near Broadus, Montana — within the existing bounds of the training complex. Four crew members ejected from the high-speed aircraft and survived.

The process of expanding the training area began in 2008. Supporters include Republican U.S. Sen. John Thune of South Dakota. He's described the expansion as vital to keeping Ellsworth Air Force Base near Rapid City open.

Some residents, state officials and politicians in Montana and North Dakota say the sheer size of the training area could cause economic harm — from disrupted medical flights and oil and gas companies unable to do aerial monitoring work in the Bakken region, to cows getting scared during calving season when planes roar overhead.

U.S. Sen. John Walsh said the government needs to balance the military's needs with "the reality of what that expansion could mean."

"Montana's pilots, landowners, farmers and ranchers have all expressed deep concern to me about the impact of having bombers overhead," the Montana Democrat said in a statement to The Associated Press.

Walsh and others in Montana — including Sen. Jon Tester, Gov. Steve Bullock and Walsh's Republican opponent in the fall election, U.S. Rep. Steve Daines — have pushed for the training area size to be curtailed. That would ease potential effects on private and commercial flights, they say.

They also want additional safety measures put in place such as better radar and communications systems that could help prevent midair collisions.