BILLINGS — Montana’s congressional delegation is pushing for changes to an Air Force proposal to establish a bomber training area over the Northern Plains that would cover an area larger than West Virginia.

A decision is due in coming weeks on the plan to expand the Powder River Training Complex over Montana, Wyoming and the Dakotas. Approval also is needed from federal aviation regulators.

The proposed expansion would quadruple the training airspace, making it the largest over the continental United States.  It would be used by B-1 bombers at Ellsworth Air Force Base in South Dakota and B-52 bombers at Minot Air Force Base in North Dakota.

Montana elected leaders and state aviation officials say the bombers would disrupt rural communities and scare livestock as they roar overhead on maneuvers, dropping flares and chaff.

Montana U.S. Sen. Jon Tester told The Associated Press that time is running out to get changes made.

“We want the Air Force to address this. They’re moving pretty darn fast right now,” Tester said. “For those guys to open up the Powder River Basin without addressing our concerns is unacceptable.”

At the prodding of southeast Montana officials worried about the expansion, Montana U.S. Sens. Tester and John Walsh and Rep. Steve Daines told Air Force Secretary Deborah Lee James in a Friday letter that the proposal would stifle economic development and threaten safety in the region.

They asked for changes including fewer restrictions on civil aircraft in the area and better radar capabilities to prevent accidents.

North Dakota lawmakers have been supportive of the proposal. They say it would stabilize the future of Ellsworth and stave off its possible closure.

Under the Air Force plan, any given location across the training area could see up to nine low-altitude overflights by military aircraft annually. Supersonic flights in the area would be limited to 10 days a year during large-scale exercises involving roughly 20 aircraft. 

As many as 78 civilian flights a day could be impacted when the large-scale exercises are conducted, shutting down the entire airspace, the Air Force said.

The Air Force acknowledged in a study released Nov. 28 that the low-altitude flights and loud sonic booms have the potential to startle ranchers, recreationists and American Indians living on four reservations in the region. 

The Air Force will make a final decision no earlier than 30 days after the study was released, said Air Force spokesman Capt. Christopher Diaz. That means a decision could come before the end of the year

A B-1B from Ellsworth Air Force Base crashed in August of 2013 in southeastern Montana near Broadus — within the existing bounds of the training area. Four crew members ejected from the high-speed aircraft and survived.